Add the Kefir Soda Starter packet to your juice and stir till dissolved. Fill the rest of the bottle with water leaving an inch of room at the top.
Allow it to ferment for 3-5 days or until bubbly and fizzy. If your home is 75°F or warmer it will usually take 3-4 days. Colder homes can take 5 days or longer, but you'll need to check it by popping the top and see if it's getting fizzy. It will start to bubble out the top if it does.
When it's done, you can pour in a glass and enjoy right away or place it in the fridge. Keep it stored in the fridge or it will continue to ferment and get overly fizzy and hard to pour. Burp daily and consume within 1-2 weeks for the best flavor and most benefit.