Tropical drinks get a bad rap as super-strong, super-sweet and super-complicated. Not this one, which combines gin—not rum!—and just a splash of ginger liqueur with fresh grapefruit and pineapple juices.
Combine all ingredients in a mixing tin. Muddle mint to release aromatics. Add cubed ice and shake until chilled. Double strain into a cold coupe glass (using a Hawthorn strainer over a fine mesh strainer to catch any mint fragments). Garnish with grapefruit peel and mint sprig.