Directions:
Put salt in a small shallow dish -- enough that it can coat the rim of a glass.
Cut 1 lime into 4 wedges. Cut the other lime crosswise into 4 round slices. Use the wedges to moisten the rims of 4 old-fashioned cocktail glasses. Dip rims into the salt and shake off any excess.
Divide lime wedges, grapefruit segments, and mint among glasses. Pour 1 ½ ounces of tequila into each glass. Smash the mixture with a muddler, pestle, wooden spoon, or whatever you can get your hands on. Top with ice and 3 ounces of Squirt each. Garnish with lime wheels.
Serve with remaining Squirt on the side so the strength can be adjusted. And once that initial shot is gone, don't be shy, add another. "That smashed deliciousness will still be there at the bottom of the glass to receive it," says Stark.