I usually brew a half gallon of ginger "tea" using fresh or dried ginger. I added a cardamom pod and some anise seed this time, but I've done other spices or just ginger before too. I use 1/2 to 3/4 cup of sucanat (unprocessed cane sugar). Once that cools to room temp, I strain the chunks, add a heaping spoonful of sourdough starter and give it a good stir. Then it goes in a couple quart-size flip top bottles on the counter for 3-7 days. It gets fizzy pretty fast, so I burp the bottles 1-2×/day. Once I like the taste I pop it in the fridge.