Peel the mango, then blend until smooth.
Add the pineapple juice, lime juice, and sweetener, then stir to combine.
Pour in the sparkling water or coconut water, depending on whether you want a lighter or creamier result.
Serving: Pour into glasses over ice, then garnish with mango, pineapple, and mint.
If you'd like a more elegant, creamier version, you can also add a little coconut milk — that way the drink becomes even more tropical.