There are dozens of variations on the basic recipe - Water, tea, and sugar combined into sweet tea, cooled, and fermented with a kombucha mother.
Here is a base I work from:
8 tea bags
3 cups of Sugar
1 cup (min) Kombucha with mother
Boil water, add sugar and tea, steep for 45 minutes.
Cool to room temperature (I use my wort chiller), add Kombucha and mother.
Ferment for one week. (Have let a batch go as long as two weeks - was very tart)
Let sit 3-5 days to carbonate.