Combine 2 cups grapefruit juice, 1/4 cup sugar and 1/2 jalapeno (with seeds) in a medium skillet; cook over medium-high heat until syrupy, about 10 minutes. Let cool, then strain. Add seltzer.
For each drink, combine 2 to 4 tablespoons flavored syrup with 1 cup cold seltzer in an ice-filled glass.
Photograph by Charles Masters
Recipe courtesy of Food Network Magazine