Blend the ripe mango into a very smooth purée. Add the sugar syrup (or simply sugar, but in that case, stir until completely dissolved) and lemon or lime juice. The amount is up to your taste and depends on the mango's sweetness and what you expect from the lemonade. Add a tiny pinch of salt, literally just a few crystals, to bring out the flavour of the mango. Mix well, pour about 50 ml into a glass and top up with sparkling water. Stir again and add a few mint leaves. Ice can be added if desired. Adjust the amount of mango purée per glass to your liking.