from Joshua Weissman - requires fermentation - https://www.joshuaweissman.com/post/fermented-ginger-beer

Ingredients:
‘Ginger Bug’ Ingredients (First Day):
    2 cups (500ml) filtered water
    2 Tbsp (22g) finely chopped or grated ginger (skin on is fine)
    2 Tbsp (28g) granulated sugar

Ginger bug feeding (every 24 hours):
    2 Tbsp (22g) finely chopped or grated ginger (skin on is fine)
    2 Tbsp (28g) granulated sugar

Ginger Beer:
    2 quarts filtered water
    1 1/4 cup plus 2 Tbsp (273g) granulated sugar *see notes*
    1/4 cup (54g) ginger, grated
    1/2 cup (110g) strained ginger bug liquid
    *optional* Juice of 3 lemons


*notes on sugar in ginger beer: You're welcome to make the ginger beer much less sweet if you prefer. I would say the lowest you can go on sugar is 1/2 cup (170g).

Preparation:
1) To cultivate your own wild yeast, combine filtered water with granulated sugar, finely chopped ginger and place in a 1-quart glass/plastic container.

2) Mix together until the sugar is dissolved, and cover with a cheesecloth. Let it sit for 24 hours.

3) Moving forward, add the same amount of ginger and sugar every 24 hours until it becomes fizzy. This should take about 2-3 days.

4) Once the ginger bug is fizzy, pour 2 quarts of water into a large pot. To that, in granulated sugar and grated ginger. Bring up to a boil and then reduce the heat to a simmer and let it sit for 5-8 minutes. Let it cool down naturally until it reaches room temperature, leaving all of the ingredients in there to steep.

5) Once it’s up to room temperature, strain your liquid through a fine mesh colander. Make sure to press out the juices.

6) Next, add in ½ cup of your strained ginger bug and the juice of 3 lemons. Mix together until thoroughly combined and transfer that mixture to some flip-top bottles. Make sure to leave 2 inches of head room.

7) Let them sit out at room temperature with the flip bottle tops locked, for 3-6 days or until they’re fizzy. 

8) Once they’ve reached that point, you can refrigerate them; but make sure you’re opening the top and burping them once a day.