Here is another great recipe from http://www.cultureforhealth.com ginger bug:

A ginger bug is the start of many natural fermented beverages. The mixture of sugar, ginger, and water captures wild yeasts and beneficial bacteria, which can then be used to add a probiotic boost (and fizz) to herbal sodas like ginger ale or root beer, and fruit sodas like blueberry, raspberry, or rhubarb. Easy to start and continue growing, this “bug” can be ready to make soda whenever you like.

Ingredients:

• 3 cups water
• 3 tsp. organic sugar
• 3 tsp. diced ginger
• Additional sugar and ginger for maintenance

Instructions:

1. Combine all ingredients in a quart jar.
2. Place a tight lid on the jar, give it a shake, and ferment in a warm spot (72-80°F) for 24 hours.
3. Every day for the next week add 2 teaspoons each of sugar and diced ginger. The liquid will begin to bubble towards the end of the week. If you’re using the classic cap-and-band jar lid, you will be able to feel the top of the lid for pressure. Once there are bubbles forming at the top of the mixture, it’s ready to use for soda making.
4. To keep the bug alive and continue growing it, feed it daily using the proportions above. Or rest it in the refrigerator and feed it 1 tablespoon each of ginger and sugar once per week. To reactivate the ginger bug for making soda, bring bug to room temperature and begin feeding it again daily (step 3, above).

Instructions for Making Cultured Sodas:

1. Mix 1/4 cup ginger bug starter into 1 quart of sweetened and flavored liquid.
2. Pour into a bottle with a tight seal, such as our Grolsch-style flip-top bottle, and ferment for 2-3 days at a warm room temperature (no more than about 85ºF).