A boozy little cocktail that's perfect for summer!
To make the sweet and sour mix, bring the water to a boil in a small pot. Stir in the sugar until dissolved and remove from the heat. Stir in the lemon and lime juice. To make the cocktail, add the sweet and sour mix, club soda, vodka, and frozen watermelon to a glass. Stir to combine. Serve immediately. Store remaining sweet and sour mix in the refrigerator, tightly sealed, for up to one week.