Freeze mint leaves in ice cube trays - one small sprig of mint in each ice cube

Make sugar syrup: Heat sugar and water in a small saucepan until sugar is melted. Put aside to cool

Remove skin from watermelon and puree fruit in blender

Push watermelon puree through a seive

combine cooled sugar syrup, watermelon juice and lemon juice

Place 2-3 mint ice cubes in each glass. Pour in the watermelon mixture until the glass is about 3/4 full. Top with sparkling mineral water. Decorate the glass with sprigs of mint or slices of lemon.