How to Make It
In a large saucepan, bring water and sugar to a boil. Add black and green tea bags and remove from heat. Let steep 15 minutes. Remove tea bags, and let sit until cool, about 30 minutes.
Pour cooled tea into gallon jar. Add starter tea and SCOBY. Cover jar with paper towels, and seal with rubber band.
Set aside, covered, for 7 days at 70°F, out of sunlight.
Pour tea into 5 glass bottles and 1 plastic bottle through funnel. Add desired flavors, and seal for 3-5 days. When plastic bottle feels right to the touch, the kombucha is ready to be consumed.
* Estimating carbohydrates, sugar numbers, and calories for homemade kombucha is tricky. The final numbers depend on how long you ferment and the "activity level" of your SCOBY. The longer you ferment, the more tart the kombucha will be and the lower the sugar number. You could ferment kombucha until there is no sugar remaining, but your kombucha would taste like vinegar. If you prefer to ferment until the kombucha is rather tangy, it'll have less remaining sugar than if you prefer to ferment shorter to keep it sweeter. A lower sugar level lowers the calories and the carbohydrates. The only way to accurately state how much sugar is in each batch is to have it lab tested. A typical commercial version contains 60 calories, 14g carb, and 4g sugars per 16-ounce bottle.