Step 1

Put water and sugar in a small pot over medium high heat.

Step 2

Bring to a boil, stirring occasionally, until sugar is fully dissolved.

Step 3

Remove from heat and add rosemary sprigs.

Step 4

Cover pot and allow syrup to steep for about 30 minutes, until it is room temperature.

Step 5

Combine rosemary syrup, grapefruit juice, and club soda in a pitcher, or in individual cups and serve immediately over ice.

Step 6

Garnish glasses with fresh rosemary sprigs and a slice of grapefruit if desired.