Water kefir is a lightly sour, fruity, faintly fizzy drink made by fermenting sugar water with water kefir grains (also called tibicos), usually with a dried fig or other dried fruit. It contains no milk, so it’s an option for people who avoid dairy, but it isn’t milk kefir made with water: the grains, microbes and drink are different. This page is the basic first fermentation; for flavoured, fizzy bottles, see our water kefir soda recipes.
What the Grains Are
Water kefir grains are translucent, jelly-like crystals made of polysaccharide, and most of the drink’s microbes live on them (Laureys & De Vuyst, 2014). The grain material is a dextran built by Lactobacillus hilgardii, whose enzyme strings sugar into the gel (Waldherr et al., 2010). In a detailed Belgian study, the main microbes were the lactic acid bacteria Lactobacillus casei/paracasei, L. harbinensis and L. hilgardii, a bifidobacterium (Bifidobacterium psychraerophilum/crudilactis) and the yeasts Saccharomyces cerevisiae and Dekkera bruxellensis (Laureys & De Vuyst, 2014). The mix differs between grain sources, so no fixed “number of strains” applies to every batch.
What Happens in the Jar
In that study, grains fermented a cane-sugar and fig-extract solution (about 7% sugar) at 21°C (Laureys & De Vuyst, 2014):
- In the first 24 hours, the sucrose fell from 47.5 to 1.2 g per litre and the grains grew from 16.4 to 28.6 g, building most of their new gel from that sugar. Sucrose being gone doesn’t mean the drink is sugar-free: splitting sucrose releases glucose and fructose, which the microbes keep fermenting over the next days.
- By 72 hours, most of the acids and alcohol had been made: pH had dropped from 4.26 to 3.45, and ethanol reached 20.3 g per litre, about 2.6% alcohol by volume. Lactic acid was the main acid, with small amounts of acetic acid, glycerol and mannitol. Fruity esters such as ethyl acetate and isoamyl acetate give the aroma.
How you brew changes the drink. Short brews favoured some bacteria and S. cerevisiae, long ones other bacteria and Dekkera; rinsing the grains between batches gave slightly more grain growth and a lighter drink, and different temperatures (17–29°C) favoured different species (Laureys et al., 2022). So brew in a steady, room-temperature spot and stop when it tastes the way you like it.
It Contains Alcohol
Water kefir is a soft drink to most people, but the 2.6% measured at 72 hours is closer to a light beer. Shorter brews make less, and a sweet second fermentation can make more. For comparison, US rules treat kombucha that reaches 0.5% alcohol or more as an alcoholic beverage (TTB). Keep that in mind for children, during pregnancy, and if you avoid alcohol.
What It Does (and Doesn’t) Do
Water kefir contains live bacteria and yeasts, but there’s very little human research on it. In one study without a control group, 40 healthy adults drank 200 ml of homemade water kefir a day for 14 days. Their gut bacteria shifted, while about a third reported flatulence and a quarter bloating (de Mel et al., 2026). That’s not evidence for immune or other health claims. Enjoy it as a lower-sugar alternative to soda, and see kombucha vs water kefir for how the two compare, or how to make milk kefir for the dairy version.