Sprinkle the mint leaves with sugar and rub them in order.
Squeeze the juice out of the lemon, orange and tangerine, leaving 2 cups to pour into glasses. (do it manually, helping with a fork).
Put 1 tsp of mint-sugar mixture in a glass. Add 4-5 ice cubes and set aside citrus cups. Pour the freshly squeezed juice (about half a cup) into a glass. Add cold filtered water to a glass.
When serving, garnish with mint leaves and serve immediately.