Prepare this delicious Grapefruit Watermelon Cocktail. We recommend using white tequila for this recipe, as añejo tequila is best enjoyed neat due to its aromas. Tequila is a Mexican spirit with a designation of origin and is produced in Guanajuato, Jalisco, Michoacán, Tamaulipas, and Nayarit. For this Grapefruit Watermelon Cocktail, we suggest using natural grapefruit concentrate, as it will give a more intense flavor to this easy-to-make drink. Enjoy an afternoon with friends with this tasty cocktail.