Hydration

What Counts as Water Intake? Tea, Coffee, Sparkling Water, Milk and Food

What counts as water intake? Tea, coffee, sparkling water, milk and even food all do. Here's what a 13-drink hydration study found, and the few drinks to limit.

By the Caffeine vs Water team · 28 September 2026 · 8 min read

If you're trying to hit a daily water goal, it matters what counts as water intake. Does your morning tea count? The flat white you had at 11? The can of sparkling water at your desk? The answer is mostly yes, and the science behind it is surprisingly clear.

The myth that caffeinated drinks "don't count" comes from caffeine being a mild diuretic. But when researchers measured how much fluid people kept after different drinks, the differences were small or absent for everything people normally drink.

What counts as water intake, drink by drink

Here's a quick reference. The hydration column is based on the Beverage Hydration Index study described below, plus guidance from the NHS and the National Academies. Caffeine figures are typical servings from our drink catalog.

The Beverage Hydration Index: what the study found

In 2016, researchers at three UK universities gave 72 healthy men a litre of different drinks over 30 minutes and collected their urine for the next 4 hours. They tested 13 everyday drinks: still water, sparkling water, cola, diet cola, hot tea, iced tea, coffee, lager, orange juice, a sports drink, full-fat milk, skimmed milk and an oral rehydration solution.

The idea was simple. If a drink hydrates less well than water, you'd pee out more of it. The results:

• No difference from water for cola, diet cola, hot tea, iced tea, coffee, lager, orange juice, sparkling water and the sports drink.
• Better than water for full-fat milk, skimmed milk and oral rehydration solution. After 2 hours, their hydration index was about 1.5, meaning roughly half as much again of the fluid was still in the body compared with water.

Milk and rehydration drinks do well because their sodium, potassium, protein or sugar help your body hold on to the fluid.

Does tea count as water intake?

Yes. Tea is almost entirely water, and in the hydration index study both hot and iced tea matched still water. A mug of black tea has around 47 mg of caffeine, roughly half a small coffee, which is far below the doses that noticeably increase urine output. Green and white tea have even less, and herbal teas have none. The NHS lists tea among the drinks that count toward your 6 to 8 glasses a day.

Our guide to caffeine in tea compares black, green, white, oolong, chai and herbal teas.

Does coffee count as water?

Yes, for normal amounts. In a 2014 study, men who regularly drank coffee spent three days having four 200 ml cups a day and three days having the same amount of water. Their total body water, blood markers and 24-hour urine volume were the same on both. The authors concluded that moderate coffee hydrates about as well as water.

The exception is a very large single dose. When regular coffee drinkers had coffee with about 537 mg of caffeine at once (6 mg per kg of body weight), their urine output nearly doubled over the next three hours. At about 269 mg, there was no change. So a regular mug or a latte counts in full; four shots of espresso in one sitting may count a little less. The full evidence is in does coffee dehydrate you?

Does sparkling water hydrate you?

Yes, exactly as well as still water. Sparkling water was one of the 13 drinks in the hydration index study, and its effect was no different from still water. The bubbles are just dissolved carbon dioxide; they don't change how your body handles the water.

If you find plain water boring, the NHS specifically suggests sparkling water, sugar-free squash or a slice of lemon or lime as a way to drink more. Flavoured sparkling waters count too, as long as you're happy with what's in them.

Does milk count as water intake?

Yes, and it's one of the most hydrating drinks there is: both full-fat and skimmed milk were retained better than water in the study. A 12 oz latte is mostly milk, with about 63 mg of caffeine from a single shot. The trade-off is calories, so most people wouldn't use milk as their main source of fluid.

What about juice, soda and energy drinks?

They all count as fluid, but they come with extras you may not want in large amounts:

• Juice and smoothies. The NHS says to limit them to one small glass (150 ml) a day, with a meal, because of the free sugars.
• Soda. Regular cola hydrated like water in the study, but a regular can carries a lot of sugar. Colas and some other sodas also have caffeine: see caffeine in soda for the numbers.
• Energy drinks. The liquid counts, but the caffeine climbs quickly. A 16 oz can of Monster has around 160 mg and some cans have 300 mg. Two or three puts you near the 400 mg daily limit. The energy drink comparison lists the big brands.

Does alcohol count?

Only with a big asterisk. A 4% lager matched water in the study, but stronger drinks weren't tested. The American College of Sports Medicine notes that alcohol can act as a diuretic, especially at high doses, and advises moderation when you're trying to rehydrate, such as after exercise. Don't count wine or spirits toward your water goal.

Does food count toward water intake?

Yes, and it's a meaningful amount. When the U.S. National Academies set its water guidance of about 2.7 litres a day for women and 3.7 litres for men, those totals included food. Around 80% of that water usually comes from drinks and 20% from food. Fruit, vegetables, soup, yoghurt and cooked grains are all mostly water.

So you don't have to drink the whole headline number. For a target sized to your body, see how much water you should drink a day.

So why does plain water still matter?

Because the other drinks bring things along with the fluid:

• Caffeine. Coffee and tea are fine for hydration, but every cup adds to the caffeine still in your body at bedtime. A 4 pm coffee counts toward your water goal and may also cost you sleep. The bedtime caffeine calculator shows how much would be left when you turn off the light.
• Sugar and calories from juice, soda and sweetened coffee drinks.

That's why many people like to drink a glass of water with their coffee: not because coffee takes water away, but because it spaces out the caffeine and keeps water on your radar. In Caffeine vs Water, every drink you log counts toward your goal, and a strong coffee simply adds one paired glass on top.

If you're unsure whether you're getting enough, the signs of dehydration are a better guide than any single rule.

Sources

1. Maughan RJ, et al. A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index. Am J Clin Nutr, 2016.
2. Killer SC, Blannin AK, Jeukendrup AE. No evidence of dehydration with moderate daily coffee intake. PLoS One, 2014.
3. Seal AD, et al. Coffee with high but not low caffeine content augments fluid and electrolyte excretion at rest. Front Nutr, 2017.
4. National Academies. Report sets dietary intake levels for water, salt, and potassium, 2004.
5. NHS. Water, drinks and your health.
6. American College of Sports Medicine; Sawka MN, et al. Exercise and fluid replacement. Med Sci Sports Exerc, 2007.

General wellness information, not medical advice. If you're pregnant, have a heart condition, or take medication that affects caffeine, check your limits with a doctor.