I will leave my recipe here. First of all you will need a starter (ginger bug). Just combine 2 Tbsp of grated ginger (with skin), 2 Tbsp of white sugar and approx. 150ml of water (room temp.) in a Mason jar. Cover the top with some fabric to make air come in and out and leave in a dark place for 1-2 days. After that you will see some bubbles coming from the bottom. Add another 1 Tbsp of grated ginger and equal amount of sugar. Wait for another 1-2 days. After 3-4 days of fermentation your starter are ready to use.
For the drink you'll need:
1.2 L of water
5 Tbsp of green tea
100 g of grated ginger
150 g of white sugar
Juice of a half lemon.
Combine all ingridients in a pan and boil for 10-15 min. Make sure to dissolve the sugar. Cool down to room temp.
Now prepare your fermenting bottle (mine was exactly 1.2 L). Add your starter liquid. Leave 10-20% of your starter for further usage. Add ginger tea and close the lid tightly. Put the bottle in a dark place at room temp. Let the microorganisms do their job for 3 days. Serve chilled. Enjoy!