Make the honey simple syrup by heating the honey and water on medium until dissolved. Reduce heat to low, stir for a minute or so and remove from heat to cool to room temperature.
For the cocktail, combine the simple syrup, rum, mint, lime juice, sparkling water and a few ice cubes in a cocktail shaker. Shake and serve over lime slices with extra mint for garnish.
Notes
Store extra simple syrup in a jar in the fridge as it will keep well for at least a couple of weeks.