Take a jalapeno pepper and cut two thin slices from it. The jalapeno that I used was quite spicy so a slice per glass was good enough. In case the one you have isn't spicy enough, feel free to add more slices.
Mix the sparkling water and mango puree in a jar. If using sugar, add that too.
Pour into serving glasses, and sprinkle with chopped mint leaves, jalapeno slice [1 per glass] and chaat masala.