Dip the rims of the cups you are using in chamoy or tajin, if desired.
Fill the cups with ice, then fill with watermelon agua fresca and serve immediately.
Notes
Storage: Refrigerate in an airtight container for up to 5 days. Stir it right before serving to redistribute the sugar. Freeze: Transfer any leftovers to a freezer-friendly bag or container and freeze it for up to 6 months. Thaw it completely in the fridge and then serve as usual when it’s no longer watermelon season.Granulated Sugar: You can use raw honey, agave syrup, light brown sugar, or dark brown sugar.Make Ice Pops: Pour the mixture into ice pop molds to make delicious frozen treats. You can even dip them in chamoy to make them tangier.Make It Fruitier: Adding 1/2 cup of strawberries or raspberries to the agua fresca will add a punch of berry sweetness.Use Frozen Fruit: Fresh watermelon gives you the best flavor, but you can also use frozen watermelon. Whether you buy frozen watermelon chunks or have leftovers from a couple of days ago, this fruit-flavored water is a great way to use up any leftover watermelon.Add Alcohol: Want to make it boozy? Add a hearty splash of your favorite liquor and this watermelon water instantly turns into a party! I like it with rum, tequila or vodka!