In a clean glass jar (about 1-quart capacity), combine the water kefir grains, organic cane sugar, and filtered, non-chlorinated water. Add the optional lemon slice and dried figs/dates for additional minerals to nourish the grains.

Cover the jar loosely with a breathable cloth (like a coffee filter or cheesecloth) secured with a rubber band. This allows airflow while keeping contaminants out.

Place the jar in a spot with stable room temperature (ideally 68-75°F / 20-24°C) away from direct sunlight. Let it ferment for 24-48 hours. The longer it ferments, the less sweet and more tart the kefir will be. Taste periodically to determine your preferred flavor.

Once the primary fermentation is complete, strain the water kefir into a clean bottle or jar, using a non-metallic strainer. Reserve the water kefir grains for your next batch (they can be stored in a fresh sugar-water solution in the fridge for up to a week if not using immediately). Discard the lemon slice and dried fruit.

For a second fermentation (F2) and flavoring, add your desired fresh fruit slices, berries, ginger, herbs, or a splash of fruit juice to the strained water kefir in the sealed bottle. Leave about 1 inch of headspace in the bottle.

Seal the bottle tightly with an airtight lid. Let it ferment at room temperature for another 12-24 hours to build carbonation. Be cautious and 'burp' the bottles (release pressure) occasionally to prevent excessive pressure buildup, especially in warmer temperatures.

After the second fermentation, strain out any fruit or herbs, if desired. Chill the flavored water kefir in the refrigerator before serving. It can be stored in the fridge for several days.