Agua Fresca de Sandia (Fresh Watermelon Drink — Mexico)

8 cups loosely packed seeded  watermelon chunks
1/4 cup packed fresh mint leaves
12 ounces sparkling water
Granulated sugar
Ice cubes
Mint sprigs, for garnish

In a blender, purée the watermelon in batches, adding the mint leaves to one of the batches. Pour the watermelon juice into a large pitcher. Stir in the sparkling water and taste. Add 1 tablespoon or more of sugar if needed. Chill for at least 1 hour.

Pour over ice in tall glasses and garnish each glass with a mint sprig, if desired.

Variation
Substitute mangoes or blood oranges for the watermelon.