Many drink mixes emphasize convenience over flavor. Here's a make-ahead combination of fresh ingredients that doesn't require a blender. Heat 1 cup sugar and 1 1/2 cups water in a small saucepan, stirring to dissolve sugar. Stir in 2 cups fresh lime juice, pour into a 9-by-13-inch metal pan, and freeze overnight. Just before serving, scrape with a spoon until slushy. Stir in 1 cup tequila. Transfer to glasses, and garnish with slices of lime.
Makes 6 drinks.