Under the right conditions, you can coax the tibicos (aka water kefir grains) to create a high-gravity (higher alcohol than normal) version of water kefir. There are now several commercial brands of kombucha employing similar techniques.
The “trick” is to feed the yeasts and provide the right conditions, which prompt the yeasts to create ethanol, and at the same time, deny the bacteria what they need to eat the ethanol. Normally, bacteria further break down the ethanol into carbon dioxide and various organic acids. Without enough oxygen (i.e. when it’s in secondary fermentation in a closed bottle), they can’t do that work, thus leaving a boozier, more adult version of water kefir.
This recipe uses a kitchen scale. Start by placing your container on a scale that is tared to zero. Right before you need to measure the next ingredient, zero the scale.
We tested this recipe and it comes in at around 3% alcohol by volume (ABV). It actually can be secondary-fermented fpr a few weeks (I think it continues to develop flavor) and poured by the glass directly from the secondary ferment vessel. It’s best served chilled.
If you’d like to understand how much alcohol is likely in your brew, then you can use a 
The original gravity (OG) of this recipe should be about 1.038 (@68F). Use a hydrometer to measure the final gravity (FG), then you can infer how boozy it is! Just note that there are other by products of fermentation in water kefir (organic acids) which alter the weight of the finished solution, so it’s not quite as accurate as measuring the gravity of beer. Usually, FG is overstated by about a factor of 2. So if you get a 4% reading, your WK has between 2% and 4% abv.
- 1 gallon filtered water
- 350g raw organic sugar
- 140g water kefir grains
- 112g fresh grated ginger
- 1 slice lemon
- ⅛ tsp. sea salt
- 3-4 g molasses
- 9.2g (about 4 to 5) dates
- kitchen scale
- muslin tea bag
- Add water to a 1-gallon or larger glass or ceramic container. You can heat the water to hasten sugar dissolution, but cool it to body temperature (100°F/37°C) or lower after dissolving sugar and before adding grains. Zero the scale.
- Measure and add sugar and dissolve in water.
- Zero the scale. Measure and stir in molasses until it dissolves.
- Add lemon and dates to container.
- Grate ginger, then add to a muslin tea bag. Capture as much of the fresh ginger juice as possible.
- Add muslin bag to container.
- Zero the scale. Measure and add water kefir (WK) grains.
- Cover with a clean dish or tea towel, or coffee filter and secure with a rubber band.
- Ferment 6 to 8 days (primary).
- Strain liquid through a fine mesh strainer or cheesecloth into swing top bottles (or other container that can seal tightly, such as one of those empty glass fancy-pants sparkling water bottles (the kind with a metal cap). The grains and fruit will be left in the strainer. Remove the fruit pieces from the strainer by hand and add to the liquid. Do not throw away the grains!
- Close the container(s) and let ferment 2 to 10 more days at room temperature. BE CAREFUL WHEN OPENING: Contents will build up pressure. Usually I let it continue to ferment at room temp one or even 2 weeks, and consume it directly from the fermenting bottle.
- Or you can move to refrigerator when you like the taste. Serve chilled.
- The grains you strained out from the primary fermentation will probably have multiplied. Add the grains to a fresh solution of sugar water by dissolving 1 Tablespoon/15 ml sugar to 1 cup/ 250ml of water. Store in the refrigerator for up to a few weeks.