A traditional drink sold by street vendors in Mexico. Substitute practically any juicy fruit in existence for the watermelon with equally refreshing results.
Puree the watermelon and water in a blender until smooth. Add agave nectar, lime juice and mezcal, if using. Adjust sweetness to taste and pulse blender to combine. Serve in a highball glass over ice with mint sprigs and lime wheels as garnish.
You can strain the agua fresca, if a thinner consistency is desired.