Boil the tea, and leave to steep for 30 minutes before removing the tea bags. Then add the sugar.
After the tea has cooled add in the scoby and cover lightly with a cloth to prevent contamination.
Leave at room temperature for at least one week (up to two weeks). After one week, taste it regularly to see if ready. It is ready once it is no longer too sweet (the scoby will have consumed the sugar) but before it is too acidic.
Store for months in the fridge. Add frozen fruit or other flavorings if desired.

2 liters boiling water
4 black tea bags
100 gram white sugar
200-250 ml previous-batch kombucha
Fruit of choice
Glass jars
Scoby