5 Drinks That Are OK To Sip While Fasting — And 5 That Will Break Your Fast Immediately

As more people try intermittent fasting in the name of better cognition or metabolic health, many questions arise about what exactly breaks a fast.

Food is an obvious culprit, but what about beverages? What (if anything) can you drink while fasting to stay satisfied? We polled fasting experts and research scientists to learn all about what you can drink while fasting without losing out on benefits.

Water is the best thing to drink while fasting. Besides the fact that water has zero calories, it also offers the human body a slew of health benefits (not to mention makes up around 60% of the human anatomy).

Physician Catherine Waldrop, M.D., previously told mbg that while a cup of black coffee1 or tea doesn't offer the body the same amount of hydration as a glass of water, she counts them toward a person's daily water intake.

This is good news if you need a caffeine fix in the morning, but you still need to be mindful of your serving size, as journalist Steve Hendricks, author of The Oldest Cure in the World: Adventures in the Art and Science of Fasting, notes the caffeine in coffee can affect your fast. However, the jury's still out on how much of an effect it has. 

Fasting researcher and professor of nutrition at the University of Illinois–Chicago Krista Varady, Ph.D., tells mindbodygreen that while adding MCT or coconut oil to your coffee will, calorically, break your fast, it shouldn't stop ketosis (the process by which the body utilizes stored fat as an energy source instead of glucose).

"They will add to your calories but can keep you feeling full," Varady says, not completely writing off the beverage option. Thurow is also not against adding MCT oil to coffee during a fasting period, as "fats are processed differently [than] other macros."

Thurlow says that as long as the sparkling or seltzer water in your fridge does not contain artificial sweeteners, you can enjoy it during your fasting window.

Soda is loaded with sugar. One cup of Coca-Cola, for example, contains 26 grams—that's 1 gram over the daily recommended sugar limit for women4. Soda is also high in calories, so you'll want to avoid sipping on this bubbly beverage during a fasting window.

As for diet, zero-calorie, or zero-sugar beverages, these are also a no-go, as they contain artificial sweeteners that can trigger an insulin response.

Alcoholic beverages can also be high in calories and sugar. Varady says drinking alcohol on an empty stomach during your fasting window is never a good idea.

Well-balanced smoothies make for a great snack or meal option, as they're loaded with nutrients, minerals, and macro and micronutrients, but they will break your fast.

Thurlow also stresses that commercially available options (prepackaged, store-bought bottles) often have "way too much sugar with little to no fiber to help slow absorption." Her advice? Wait until your fasting period is over and either make your smoothie at home or opt for a piece of fruit.

Again, although packed with nutrients, bone and vegetable broths are caloric beverages that will fire up your digestive system. These warming beverages should be avoided if you're sticking to a fast.

That said, Thurlow notes that for patients undergoing medically supervised longer fasts (i.e., for a procedure like a colonoscopy), these types of broths might be on the approved-to-consume list, as they contribute to a healthy gut and contain protein. Also, drinking bone broth is a great way to break your fast, as the liquid is light on your stomach.

According to Thurlow, you're better off taking your coffee black or with MCT oil or coconut oil if you can. "I don't love butter or milk, as they are insulinemic (they will spike insulin)," Thurlow says.

In short, yes. Consuming anything caloric will technically break a fast. However, whether or not drinks that are low in calories "count" as breaking your fast depends on the type of fast you're following and how strictly you're following it.

There are many types of fasting, but the most common is time-restricted eating, during which participants limit the window of time they can eat to a set number of hours each day. How long you fast (10 hours, 16 hours, 18 hours, 20 hours, sometimes even 24 hours) will be determined by your age, health, lifestyle, and, of course, your health goals.

In a 5:2 fast, a person eats as they normally would for five days out of the week and is restricted to 500 to 600 calories per day for the remaining two days.

This type of fasting has been shown to aid in weight loss5, enhance cognitive function6, and support an individual's cardiometabolic health7.

On fasting days, you'll want to stick to water, tea, and black coffee because they're low in calories and sugar-free. You're better off saving your calories for (and focusing on nutrition during) your meals. On normal eating days, feel free to incorporate other healthy beverages like smoothies or bone broths to the rotation, but still do your best to avoid sugary sodas or juices.

The 16:8 intermittent fasting plan is a popular one for beginners because it offers fasters a longer feeding window (fast for 16 hours, feed for eight). It's known for aiding in weight loss8 and lowering cholesterol9.

Because you have more time to eat during a 16:8 fast compared to other plans, it might be best to be stricter when you are in your fasting window. Stick to zero-calorie beverages like water or sparkling water if you can.

The 18:6 intermittent fast is a more restrictive option, as you fast for 18 hours and feed for six. For reference, according to the U.S. Bureau of Labor Statistics, as of 2020, the average individual between the ages of 25 and 45 years old was, on average, awake for 14 to 15 hours. That's nine hours of awake fasting hours.

According to Madiha Saeed, M.D., author of The Holistic Rx, it's crucial to stay hydrated throughout this longer window. In a previous article, Saeed told mindbodygreen that if you get tired of plain water, green and black teas, as well as ginger and other herbal options, can help keep you hydrated and support electrolyte function in the body.

Daylong fasts are generally religious customs (Mormons fast for 24 hours at a time, while the 36-hour fast has been nicknamed the Monk fast for its ties to Hinduism) or medically prescribed. Research suggests that 24-hour fasts once per month can lower mortality rates and lower a person's risk of heart failure.

To reap the full benefits of this intense fast, most people will want to stick with zero-calorie beverages. However, you should always work with a doctor before attempting an extreme fast like this.

With reverse fasting, the fasting window begins around 5 or 6 p.m. and lasts 12 to 15 hours. It too has some significant science-backed results, including a reduction in breast cancer recurrence10. According to integrative medicine doctor Amy Shah, M.D., water or low-calorie liquids of up to 20 calories are ideal during the fasting period.

Guzzling down glasses of plain H₂O for hours at a time can get old fast. However, for the best results, many experts believe that cutting out all caloric beverages before your feeding window will deliver the most results.

"When you fast on water only, the body gets a complete break from the very heavy work of processing nutrients," Hendricks explains. "From clinical observations, it seems that the body heals more quickly11 and perhaps more thoroughly when it has this complete break than when it doesn't."

Depending on your goals and the type of fast you're doing, drinking beverages with a small number of calories (such as lemon water or coffee) should not interfere with your progress. In fact, taking a "dirty" fasting approach to beverages can make fasting easier to stick with for beginners and help keep your body properly hydrated.

As Varady explains of her clinical experience with fasting, "Many of our studies run six to 12 months, and we want our subjects to feel comfortable while doing fasting. If we ask them to change their eating habits too much, they often drop out." Plus, she adds, if weight loss is the goal, "these additives only contribute a very small amount of calories, so it does not upset their progress."

That said, high-calorie or high-sugar options like smoothies, soda, or broth will likely do more harm than good and should be avoided during your fasting window.

And despite the health benefits of fasting, it's definitely not for everyone. For example, some experts warn that intermittent fasting is trickier for women because fasting is a type of stressor, and women process stress differently than men.

Pregnant and breastfeeding women are advised not to intermittently fast. There's also debate over what age groups should try fasting. Though there isn't enough research to suggest women over 50 shouldn't intermittent fast, Varady thinks that elderly individuals over the age of 70 should not follow this way of eating.

Varady also stresses that "individuals with a history of eating disorders as well as individuals who are at risk for developing eating disorders" should not intermittent fast "because it might exacerbate their eating disorder symptoms14."

There are a few adverse side effects to take into consideration when fasting, such as headaches and constipation15, according to Varady. Research also suggests more serious side effects could manifest in people with Type 2 diabetes, who could become hypoglycemic16 while fasting.