Lacto-fermented blueberry soda is not only easy to make at home, it's also a healthful alternative to sugar and chemical-filled commercial sodas.
Simmer blueberries and sugar in water for about 20-30 minutes.
Cool to room temperature and strain out the blueberries.
Transfer what’s now essentially blueberry juice to a 2 quart glass ball jar or demijohn.
Add whey and let it ferment for at least 3 days. Look for visible signs of fermentation via a slight fizziness. You can let it go longer if you’d like a less sweet soda as the bacteria will continue to feed on the sugars. I let mine go about 5 days but you can go as long as 10 days. Taste the soda as you go to get the sweetness you desire.
Transfer blueberry soda to soda bottles.
Keep the soda bottles at room temperature and check every day. Make sure to open the bottles every day to let some of the gasses escape. After a few days, you can move the bottles to your refrigerator where the fermentation will dramatically slow down.