Make the rosemary simple syrup. Combine water and sugar in a small saucepan over medium heat. Stir until the sugar dissolves.
Add rosemary sprigs to the syrup. Remove from heat and let steep for 15 minutes.
Strain the syrup and let it cool completely. Store extra syrup in the refrigerator.
Fill a cocktail shaker with ice. Add grapefruit juice, orange juice, lemon juice, and rosemary simple syrup.
Shake vigorously for 15 seconds.
Strain into a tall glass filled with ice.
Top with sparkling water and stir gently.
Garnish with a fresh rosemary sprig and orange wheel.
Notes
Keep leftover rosemary simple syrup in an airtight container in the refrigerator for up to 2 weeks.For a sweeter drink, add more simple syrup. For less sweetness, reduce the syrup amount.Fresh-squeezed citrus juices make a big difference in taste compared to bottled juices.Make sure to strain the simple syrup well to remove any rosemary leaves.