Yes. In a 2016 study that compared 13 drinks, sparkling water was kept by the body just as well as still water. Count it exactly like water: a 330 ml can adds 330 ml. The same was true for cola and diet cola.
Does sparkling water hydrate you as well as still water? It's one of the simplest questions about drinks, and one of the few with a clean, measured answer. When I built Hydra I needed a number for every drink in the list, and for sparkling water the study left nothing to argue about. Bubbles or no bubbles, water is water.
What the study found
The study that settles this is the 2016 work that created the beverage hydration index. Volunteers drank about a litre (34 oz) of one of 13 drinks, on different days, and the researchers measured how much of it their bodies kept over the next four hours. Still water was the reference, the drink everything else was compared with.
Sparkling water came out not different from still water. Neither did cola, diet cola, tea, coffee, lager or a sports drink. The drinks that were kept better were an oral rehydration solution, full-fat milk, skimmed milk and orange juice, which carry protein, sugar, sodium or potassium that slow down how fast the water leaves your body.
Carbonation simply isn't one of those things. The bubbles are carbon dioxide dissolved in the water, and once you've drunk it, the water behaves like any other water.
Sparkling water, soda and cola compared
Here's how the fizzy drinks from the study compare with still water, and how much a 330 ml can (about 11 oz) adds to your day in Hydra:
| Drink | In the 2016 study | Hydra factor | 330 ml adds |
|---|---|---|---|
| Still water | The reference | ×1 | 330 ml |
| Sparkling water | Same as water | ×1 | 330 ml |
| Cola | Same as water | ×1 | 330 ml |
| Diet cola | Same as water | ×1 | 330 ml |
| Sports drink | Same as water | ×1 | 330 ml |
| Milk | Kept better, about 1.5 | ×1.2 | 396 ml |
The milk row is there for contrast. It's one of the few drinks that really does beat water, and I explain why Hydra counts it ×1.2 rather than the measured 1.5 in does milk hydrate better than water.
What about soda and cola?
For hydration alone, cola and diet cola did the same as still water in the study, so Hydra counts soda ×1. Cola has some caffeine, but in normal amounts caffeine doesn't undo the water in the drink. I went through that in detail in whether coffee dehydrates you, and the same reasoning holds for a can of cola.
Sugar is a different question. Whether a sugary drink fits your diet has nothing to do with how well it hydrates, and it isn't something I'll pretend to answer with hydration numbers. Hydra counts the water; what else is in the glass is your call.
How to log sparkling water in Hydra
You have two easy options, and they count the same:
- Plain sparkling or mineral water: log it as Water. It counts ×1.
- Flavoured fizzy drinks, cola, tonic, lemonade: log them as Soda. Also ×1.
Both land at the same net hydration, so you can't get this wrong. The only reason to pick one over the other: History shows which drinks helped you most, and logging soft drinks as Soda keeps them in their own row there.
If bubbles help you drink more, use them
Here's the practical side. The best drink for reaching your goal is the one you actually enjoy. If plain still water bores you and a cold sparkling water doesn't, that's a perfectly good way to drink more. Hydration-wise you lose nothing.
The idea that every glass must be plain still water is a cousin of the old "8 glasses a day" rule, which turns out to have no traceable scientific origin. I wrote about that in whether you really need 8 glasses of water a day. What matters is the total that your body keeps, from every drink.
For more small tricks that make the total easier to reach, see how to drink more water every day.
How much should you drink in total?
Sparkling or still, the amount depends on you: mostly your weight, then your sex, how active you are and your climate. Hydra starts from 33 ml per kg of body weight (about 0.5 oz per lb) and adds or removes a little for the rest. A 70 kg adult who is slightly active in a temperate climate lands at about 2 500 ml a day (about 85 oz) from drinks.
To get your own number, the water intake calculator uses the same formula as the app and shows each part of the goal.
What to take from it
- Sparkling water hydrates exactly like still water. The study found no difference.
- Cola and diet cola also came out like water. Hydra counts soda ×1.
- Sugar is a separate question from hydration.
- Log plain sparkling water as Water, flavoured fizzy drinks as Soda. Both count in full.
- If bubbles help you drink more, enjoy them.
Still or sparkling, every glass counts
Hydra counts every drink by how much of it your body keeps, from sparkling water to coffee and milk. Free on iPhone and Apple Watch.
