Begin by preparing the rosemary-infused syrup. In a small saucepan, combine water and sugar. Bring the mixture to a gentle simmer over medium heat to let the sugar dissolve. Remove from the heat, add rosemary, and let it sit for about 5 minutes, allowing the rosemary to infuse its flavors into the water. Let it cool and remove the rosemary sprigs.
¼ cup granulate sugar, ¼ cup water, 2 sprigs fresh rosemary
Squeeze the juice from each fruit in a mixing bowl.
1 grapefruit, 2 limes
Fill two glasses with ice cubes, filling them about halfway, and pour the grapefruit mixture over the ice, with the rosemary simple syrup to taste.
ice cubes
Finally, pour the sparkling water into each glass, filling them to the top. Serve immediately.
1½ cups sparkling water
Notes
You could also add your favorite alcohol (or white wine!) of choice to make it a grapefruit lime cocktail.