Preparation Pour some kosher salt on a plate. Rub half of rim of a highball glass with a grapefruit wedge; dip rim of glass in salt. Combine 1/4 cup fresh grapefruit juice, 1 tablespoon fresh lime juice, and 1 teaspoon sugar in glass; stir until sugar is dissolved. Stir in 1/4 cup mezcal or tequila, add ice, and top off with 1/4 cup club soda. Garnish with grapefruit wedge.