The base of kombucha is black tea which means that it contains caffeine.
The beauty of water kefir is that it has no caffeine, however if you want a caffeinated drink then kombucha is for you.
With that said, tea is not only black and caffeinated but it can also composed of herbs and spices and those are AMAZING to add to water kefir recipes!
Now you can add black tea into your second ferment no problem. Herb teas on the other hand, contain chamomile, peppermint, berries, fruits etc. and make for lovely additions to your second ferment. You can tear the tea bag open and pour the leaves and fruit into your second ferment. Or in the case of loose teas like David’s Teas, you just add the combinations straight into your swivel top bottle.
Never add them to your first ferment. You will confuse your grains and they won’t flourish. They will actually begin to disintegrate. Your first ferment should only ever consist of water, sugar and water kefir grains.