Make the simple syrup by heating equal parts sugar and water in either the microwave or on the stove. Heat until the sugar is dissolved, then transfer to a heat-safe container and allow it to cool.

To a cocktail shaker, add the mint leaves. Lightly muddle until they are aromatic. Add the rum, lime juice, simple syrup, and ice. Shake.

Add ice to a glass, and strain the cocktail into the glass. Top with Klarbrunn Lime Sparkling Water. Garnish with lime wedges or mint leaves, and serve.