Take 500 grams of watermelon, remove the seeds and cut it into small pieces.
In a blender, add the watermelon pieces, 10-12 fresh mint leaves, 2 tablespoons of sugar, and 1 tablespoon of lemon juice. Blend until smooth.
Strain the mixture through a sieve to remove any pulp.
Pour the juice into a glass, add a few ice cubes and garnish with a sprig of mint and a slice of lemon. Your Watermelon Mint Cooler is ready to serve.