
Rub the rim of a glass with a slice of lime or grapefruit and dip in salt to salt the rim. Fill the glass with ice cubes and place in the freezer.
Combine tequila, grapefruit juice, and simple syrup with ice in a cocktail shaker. Shake until well chilled.
Pour grapefruit juice over ice in the glass. Top with club soda and a squeeze of fresh lime juice.
Serve with lime wedges.