In a cocktail shaker with ice, combine syrup, bitters and grapefruit juice, then shake. Add cold sparkling water to shaker, then immediately pour into a glass. Express grapefruit peel over drink, then garnish with it.
In a cocktail shaker with ice, combine syrup, bitters and grapefruit juice, then shake. Add cold sparkling water to shaker, then immediately pour into a glass. Express grapefruit peel over drink, then garnish with it.