What Can You Drink While Fasting?
Water, black coffee and plain tea fit a zero-calorie fast; diet soda adds little or no energy. See what you can drink while fasting and what ends a fast.
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- Blimbi Editorial
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Water, black coffee, plain tea and herbal infusions fit a zero-calorie fast; diet soda adds little energy. Juice, milk, cream and sugary drinks end it.
- The rule is energy: cited trials allowed no calories, only water and energy-free drinks.
- Water, black coffee, plain tea and herbal infusions fit a zero-calorie fast.
- Milk, cream, juice and sugary drinks add energy.
- Caffeine from coffee, tea, cola and energy drinks adds up.
Which drinks break a fast?
Anything with energy does. Here’s how the common ones compare, from plain water to a splash of milk.
| Item | Breaks the fast? | Context |
|---|---|---|
| Still or sparkling water | No | No energy; one 12-month trial encouraged plenty of it during the fast.Source 1 |
| Water with a slice of lemon or lime | It depends | A trace of energy; on a strict fast, keep water plain.Source 3 |
| Black coffee (hot, iced or cold brew) | No | Treated as energy-free in a 12-month fasting trial; caffeine still counts.Source 1 |
| Black, green, white or oolong tea, no milk | No | Treated as energy-free; contains caffeine.Source 1 |
| Plain herbal infusion | No | Essentially no energy; some blends add sugar or dried fruit. |
| Diet or zero-sugar soda | No | Little or no energy; one trial allowed up to two a day.Source 1 |
| Sugar-free energy drink | It depends | Little energy, but about 80 mg of caffeine per 250 ml can.Source 4 |
| Coffee or tea with sugar, honey or syrup | Yes | Sugars provide energy. |
| A splash of milk, cream or a plant drink | Yes | Small, but still energy, even unsweetened.Source 5 |
| Fruit juice, smoothies or coconut water | Yes | Natural sugars; save them for the eating window.Source 3 |
| Regular soda or tonic water | Yes | Contains sugar, so the fast ends.Source 2 |
Why does energy decide it?
Because that’s how the fasting trials behind this list ran their fasts: no calories, with water and energy-free drinks allowed. Temperature, brand and flavour don’t change the answer.
In a 12-month randomized trial of eating only between noon and 8 p.m., participants were encouraged to drink plenty of water and could have energy-free drinks such as black tea, coffee and diet sodas (up to two a day) during the 16-hour fast.Source 1
In the 12-week TREAT trial, the time-restricted group was told to eat from 12:00 to 8:00 p.m. and to completely abstain from caloric intake for the rest of the day.Source 2
Mixed evidence
How the trials defined the fast
TREAT asked participants to avoid all caloric intake outside a noon-to-8 p.m. window; a 12-month trial allowed energy-free drinks, including up to two diet sodas a day. Neither tested a small calorie allowance, so a splash of milk or a slice of lemon is a personal choice, not a research threshold.Source 2Source 1
How much caffeine is too much?
Coffee, tea, cola and energy drinks can all fit a fast, but their caffeine lands in one daily total. Extra cups to push through hunger can take you past it without noticing.
NHS estimates about 100 mg of caffeine in a cup of instant coffee and about 75 mg in a cup of black or green tea, and advises no more than 200 mg a day during pregnancy.Source 4
A systematic review of 381 studies concluded that up to 400 mg of caffeine a day is generally not associated with overt adverse effects in healthy adults; data for children and adolescents were limited.Source 6
| Drink | Estimated caffeine |
|---|---|
| Cup of instant coffee | About 100 mg |
| Cup of black or green tea | About 75 mg |
| Can of cola | About 40 mg |
| 250 ml energy drink | About 80 mg |
| Peppermint, chamomile or rooibos infusion | Usually caffeine-free |
Who should check first?
This list covers drinks only; gum, supplements, electrolytes and medicines raise different questions, and nothing here is a reason to start, stop, delay or change a medicine.
Frequently asked questions
The detail behind each row lives in the drink guides: water and lemon water, coffee, tea, milk and cream and diet soda. For how much to drink across the day, see hydration during intermittent fasting.
Talk to a qualified health professional before fasting if you are pregnant or breastfeeding, under 18, living with or recovering from an eating disorder, have diabetes, take insulin or a medicine affected by meal timing, are an older adult, or are acutely ill. Do not change the dose or timing of any medicine without your clinician. See Blimbi’s safety guide.
Frequently asked questions
Can you drink water while fasting?
Yes. Plain water, still or sparkling, has no energy, and a 12-month fasting trial encouraged participants to drink plenty of it during the 16-hour fast.Source 1
Sources
Time-Restricted Eating Without Calorie Counting for Weight Loss in a Racially Diverse Population: A Randomized Controlled TrialShuhao Lin et al. American College of Physicians, July 1, 2023.DOI: 10.7326/M23-0052 · PMID: 37364268Human randomized trial
Effects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity: The TREAT Randomized Clinical TrialDylan A. Lowe et al. American Medical Association (AMA), November 1, 2020.DOI: 10.1001/jamainternmed.2020.4153 · PMID: 32986097Human randomized trial
Water, drinks and hydrationNHS. NHS, May 17, 2023.Official guidance
Foods to avoid in pregnancyNHS. NHS, June 15, 2026.Official guidance
Dairy and alternatives in your dietNHS. NHS, December 11, 2023.Official guidance
Systematic review of the potential adverse effects of caffeine consumption in healthy adults, pregnant women, adolescents, and childrenDaniele Wikoff et al. Elsevier BV, November 1, 2017.DOI: 10.1016/j.fct.2017.04.002 · PMID: 28438661Systematic review and meta-analysis
Fasting Safely with DiabetesMartin M. Grajower. National Institute of Diabetes and Digestive and Kidney Diseases, August 26, 2020.Official guidance