Add the water, sugars, and lemon slices to a non-reactive container (i.e. not metallic). Stir until the sugars dissolve, and let the water cool to lukewarm, about 115Fº (45Cº)—it should be warm, but not hurt when you sprinkle a few drops on your wrist.

Stir in the yeast. Let the mixture stand in a warm spot 8 to 10 hours, or overnight, until tiny bubbles appear around the edges of the container (read the notes in my original post about this step).

Strain the liquid into two 1-quart glass jars, discarding the lemon slices. Place 4 raisins in each jar. Close tightly with lids, and let stand at room temperature until the raisins have swelled, and risen to the top, anywhere from 8 hours to 2 days, depending on the temperature in your house (this is how you know the Sima has fermented enough).

Chill until very cold. Sima will keep in the fridge for at least 1 month.