Add 2 quarts (liters) water to a large (1 gallon or more) glass or ceramic container. You can warm the water first (up to 100°F/37°C).
Add sugar and molasses to water and stir until it dissolves.
Slice ginger into thin slices, or grate it and add it to a muslin tea bag. Add slices or bag to container.
Add water kefir (WK) grains.
Cover with a clean dish or tea towel, or coffee filter and secure with a rubber band.
Store in a warm place for 1 to 2 days. (Taste it after 1 day and if you like it, you're ready to bottle and/or secondary ferment.)
If you used a bag for the ginger, remove it from container, and squeeze to get every last drop of gingery goodness. Compost the spent ginger.