Fill an 8-cup blender with ice and crush slightly to make room for liquids. Add the juice from 2 lemons and 3 limes (totaling about 1/2 cup), 1/2 cup simple syrup (you can make by dissolving 1 cup sugar in 1 cup hot water), and 8-ounces gin. Blend until ice is crushed completely. Makes 6 drinks.
If you love the tartness of fresh lemon and lime, steep 4 wide strips of both lemon and lime zest in the simple syrup solution while making it and remove when mixture is cool (before blending). If using store-bought lemon or limeade (which we don't suggest), skip the sweetener.