Combine the water and raisins in a jar with a tight lid. Be sure to use non-oil coated raisins. Sterilize the jar. If it's too much trouble to boil it, rinsing it out with boiling water should do the trick.

The next step is to wait. The fermentation period varies depending on the temperature. It should take anywhere from 2 to 4 days. Gently shake the jar and open the lid once a day.

The raisins should become plump from absorbing the water, and they will fizz as they ferment. If they fizz loudly when the jar is opened, it's ready!