Combine the warm filtered water and granulated sugar in a clean, large glass jar. Stir well until the sugar completely dissolves.

Add your chosen fresh fruit or fruit juice to the sugar water. Ensure the fruit is clean.

Cover the jar loosely with a clean cloth, paper towel, or a lid that is not airtight, allowing some air circulation. This prevents anaerobic conditions too quickly and allows gas to escape.

Place the jar in a warm spot at room temperature (ideally between 68-75°F or 20-24°C) for 24 to 48 hours. The warmer the temperature, the faster the fermentation. You should start to see small bubbles forming and the liquid will become slightly fizzy.

Taste the soda periodically after 24 hours. When it reaches your desired level of sweetness and fizziness, it's ready. If it ferments too long, it can become overly tart or alcoholic.

Once ready, strain the soda through a fine-mesh sieve into clean, airtight bottles to remove any fruit solids. Leave about an inch of headspace in each bottle.

Seal the bottles tightly and immediately transfer them to the refrigerator. Chilling will slow down the fermentation process significantly.

Serve your homemade probiotic soda cold and enjoy! Be mindful when opening, as carbonation can still build up.