To make Kombucha:
Boil 2 litres of filtered water.
Pour into a heat proof bowl.
Add 3 green tea bags (or 3 to 6 regular tea bags) and brew for 10 minutes.
Remove bags and stir in 2 cups sugar until dissolved.
Cover and leave to cool to room temperature.
Now you're ready to set up a brew or switch a ready to drink brew and set up the next batch.
Your first brew:
Pour the cooled tea into a large glass vessel. Add a SCOBY or some ready-made kombucha. Cover with muslin cloth and a rubber band, or loosely cap. If using a SCOBY, taste a little each day from Day 3 onwards, until you like the flavour - not too sweet, but not too bitey either, then switch the batch as below. If you are not starting with a SCOBY, leave the first brew until a SCOBY forms, then set up a new batch as below.
Setting up a new batch:
Remove the SCOBY from the top of your brew and set on a clean plate. Fill a coffee cup with 300ml of kombucha from the jar. Pour the rest of the kombucha into clean bottles - expect that it may fizz and froth as you are doing so. Cap and refrigerate. Rinse glass vessel, pour in new tea brew and mug of kombucha, gently place SCOBY back into vessel - it may sink temporarily, but will soon come back to floating on the top.
Cover as above, and set on the counter out of the way. Taste from time to time until you know how long a batch takes to get to the point you like it. The longer you leave it, the more sugar will have been consumed by the SCOBY. If you leave it too long, you'll have vinegar. I find that in summer it takes about 5 days to be ready, and in winter 8, but I like it with minimal sweetness remaining.
If you do happen to make a batch of vinegar, keep it in old plastic bottles and use in cleaning, as a hair rinse or similar. Kombucha vinegar has many uses!
If you haven't drunk the last batch, then you might leave a brew going to the vinegar stage on purpose every now and then, keeping the SCOBY alive as well as making a fine useful if not so tasty product. :-)
A fermented drink made with tea, sugar, and a SCOBY, kombucha has many variations and is a healthy probiotic. I use green tea these days. SCOBY stands for "symbiotic culture of bacteria and yeasts." If you don't have one, you can grow your own by using purchased raw kombucha drink from a health store, and mixing it with a brew as below - over time, a SCOBY will start to form. SCOBYs constantly grow and thicken - every now and then one peels it apart and discards a layer. Or gives that layer to a friend as their own starter SCOBY - that's how I got mine. :-)
NOTE: always work with very clean hands and equipment - you don't want to contaminate the SCOBY with unwanted species of bacteria.
To drink: Try kombucha neat, or dilute with water. I prefer it about half and half, give or take depending how tart a batch is.