1 1/4 cups fresh white, ruby red, or pink grapefruit juice
Special Equipment: Cheese cloth
Directions
Working in batches, purée watermelon in a blender until smooth. Pour into a large bowl and let stand for 10 minutes. Skim foam from surface and discard.
Set a fine-mesh sieve over a large pitcher; line sieve with cheesecloth. Strain purée into pitcher (you should have almost 7 cups juice). Stir in grapefruit juice.
Fill glasses with ice. Divide agua fresca among glasses.
