Combine sugar and water in a saucepan.

Bring to a boil over high heat.

Reduce heat and simmer until sugar dissolves.

Turn off heat and cool syrup to room temperature.

Refrigerate syrup in an airtight container for up to a week.

Combine tequila, lime juice, grapefruit juice, Campari, bitters, and simple syrup in a shaker with ice.

Shake vigorously.

Fill an old-fashioned glass with ice.

Strain the cocktail into the glass.

Garnish with a lime wheel.