Juice/Bottle
100 ml
Bottles
6
2F Time
24–48 hr
+ 400 ml finished water kefir per bottle
3,000 ml
600 ml
24–48 hr
~2.5 PSI
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Inputs
Result
20% of 500ml = 100ml juice per bottle. Kefir = 500 − 100 = 400ml. Total = 6 × 500 = 3,000ml. Medium carbonation = 24–48 hours.
Inputs
Result
30% of 1000ml = 300ml juice per bottle. Kefir = 1000 − 300 = 700ml. Total = 4 × 1000 = 4,000ml. High carbonation = 48–72 hours.
Add 10–30% juice by volume to each bottle of finished water kefir. A medium ratio of 20% works well for most juices — that is 100ml of juice per 500ml bottle. Higher-sugar juices like grape (16g sugar per 100ml) carbonate faster. Lower juice ratios (10%) give subtle flavor; higher ratios (30%) give bold flavor and faster carbonation.
| Juice Ratio | Juice per 500ml | Flavor | Carbonation Speed |
|---|---|---|---|
| Light (10%) | 50 ml | Subtle | Slower |
| Medium (20%) | 100 ml | Balanced | Standard |
| Strong (30%) | 150 ml | Bold | Fast |
Second fermentation (2F) takes 12–72 hours at room temperature depending on desired carbonation level. For gentle fizz, 12–24 hours is enough. For standard carbonation, 24–48 hours. For very fizzy soda-like carbonation, 48–72 hours. Always use pressure-rated bottles (flip-top or thick glass) and burp daily to prevent explosions.
Grape juice is the most popular choice due to its high sugar content (16g per 100ml) which produces excellent carbonation and a sweet fruity flavor. Other popular options include apple juice, mango juice, and berry puree. Ginger juice adds spice but has low sugar (4g per 100ml), so it carbonates slower. Avoid juices with preservatives as they inhibit fermentation.
Bottle explosions happen when CO2 pressure exceeds the bottle's tolerance. Use flip-top glass bottles rated for carbonated beverages. Leave at least 1 inch of headspace. Burp bottles every 12–24 hours by briefly opening and resealing. Refrigerate after desired carbonation is reached — cold temperatures slow CO2 production. Never use regular glass jars.
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Read our guide
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Last Updated: Mar 19, 2026
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