Plain water kefir is only lightly sparkling. To turn it into a fizzy, flavored soda you give it a second fermentation: bottle the finished water kefir with a little fruit juice, fruit or sugar, seal it, and leave it at room temperature for a day or two. The yeasts in it eat the added sugar and make carbon dioxide, which has nowhere to go and dissolves into the drink. Then refrigerate it to stop the fermentation. The recipe card below has the method; the table has 12 flavors to try, each for one 16 oz (500 ml) bottle.
What Water Kefir Is
Water kefir is made by fermenting sugar water, usually with dried figs and lemon, using translucent water kefir “grains” for 2–4 days. In a detailed study, the grains carried most of the microbes – lactic acid bacteria such as Lactobacillus casei/paracasei, L. hilgardii and L. harbinensis, bifidobacteria, and the yeasts Saccharomyces cerevisiae and Dekkera bruxellensis. Almost all the sucrose was broken down within 24 hours (from 47.5 to 1.2 g per litre), the pH fell from 4.26 to 3.45, and the main products were ethanol and lactic acid (Laureys & De Vuyst, 2014). How long you leave it, the temperature, and whether you rinse the grains all change which microbes dominate and how sour or yeasty it gets (Laureys et al., 2022). For making the base, see our water kefir guide.
Water Kefir Contains Alcohol
The yeasts that make water kefir fizzy also make alcohol. In the same study, ethanol reached 20.3 g per litre after 72 hours of first fermentation – about 2.6% alcohol by volume, close to a light beer (Laureys & De Vuyst, 2014). Home batches vary a lot, and a second fermentation with extra juice or sugar can add more. For comparison, in the US, kombucha that reaches 0.5% alcohol or more is regulated as an alcoholic beverage (TTB). So don’t think of homemade water kefir soda as a children’s drink, and skip it if you’re pregnant, driving, or need to avoid alcohol for any reason. Shorter, cooler fermentations and refrigerating promptly keep the alcohol lower.
Don’t Let Bottles Explode
Pressure builds quickly in a sealed bottle, and glass that isn’t made for it can shatter.
- Use swing-top (flip-top) bottles made for carbonated drinks, never decorative or cracked glass.
- Leave 1–2 inches (3–5 cm) of headspace.
- Fill one small plastic bottle from the same batch: when it’s rock-hard to squeeze, all the bottles are ready to refrigerate.
- “Burp” glass bottles every 12 hours in warm weather, and refrigerate within 24–48 hours.
- Chill before opening, and open slowly over the sink with the bottle pointed away from you.
More sugar, a warmer room and a longer time all mean more fizz – and more pressure and alcohol. Juice-heavy flavors such as grape and orange build up pressure fastest.
12 Flavor Ideas
For each 16 oz (500 ml) bottle, add the flavoring and top up with finished water kefir (grains removed), leaving the headspace.
| Flavor | Add to the bottle | Second ferment | Notes |
|---|---|---|---|
| Grape | 2 oz (60 ml) 100% grape juice | 24–36 h | High fizz; Concord juice tastes most like grape soda |
| Mango passion fruit | 3 oz mango juice + 1 oz passion fruit juice | 24–36 h | Strain if using purée |
| Strawberry lemonade | 3 muddled strawberries, juice of ½ lemon, 1 tbsp sugar or honey | 24–48 h | Strain when pouring |
| Cherry “cola” | 2 oz tart cherry juice, ¼ tsp vanilla, pinch of cinnamon, 1 tbsp honey or maple | 24–36 h | |
| Ginger lime | 1-inch ginger, thinly sliced, juice of 1 lime, 1 tbsp sugar or honey | 24–48 h | Ginger gives lively fizz |
| Orange creamsicle | 3 oz orange juice, ¼ tsp vanilla, 1 tbsp sugar or honey | About 24 h | Builds pressure fast |
| Grapefruit rosemary | 3 oz grapefruit juice, 1 bruised rosemary sprig, 1 tbsp honey | 24–36 h | |
| Lavender lemonade | Juice of 1 lemon, 2 tbsp honey steeped with ½ tsp culinary lavender | 24–36 h | Strain the lavender |
| Mint mojito | 8–10 muddled mint leaves, juice of 1 lime, 1 tbsp sugar | 12–24 h | Short time keeps mint fresh |
| Hibiscus berry | 3 oz double-strength hibiscus tea (cooled), 1 tbsp berry juice or 3 muddled raspberries, 1 tbsp honey | 24–36 h | Deep red |
| Apple pie | 3 oz apple cider (juice), ¼ tsp cinnamon, pinch each of nutmeg and allspice, 1 tbsp maple syrup | 24–48 h | |
| Strong ginger beer | 2-inch ginger, grated or juiced, juice of ½ lemon, 2 tbsp sugar or honey | 12–24 h max | Very active: burp every 8–12 h |
Is It Good for You?
Water kefir contains live bacteria and yeasts, but there’s very little human research. 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 (more Bifidobacterium and some butyrate-producing species), while about a third reported flatulence and a quarter bloating, and most noticed no change (de Mel et al., 2026). It’s a less sweet alternative to soda, not a health treatment. Compare it with other fizzy ferments in kombucha vs water kefir, kombucha second fermentation, ginger beer and Mexican tepache.
