Add pink grapefruit juice and fresh lime juice to the glass.
Stir in simple syrup until combined.
Top with sparkling water, soda water, or club soda and give a gentle stir.
Garnish with mint leaves and a grapefruit slice or lime wedge.
Notes
Use 100% unsweetened pink grapefruit juice for the best flavor. Adjust lime to taste depending on the tartness of your grapefruit. Swap in agave or maple syrup for a different sweetness profile, or rosemary simple syrup for a subtle herbal note.