In a blender, combine the chopped pineapple and strawberries. Blend until smooth.

Strain the blended mixture through a fine mesh sieve into a large pitcher to remove the pulp, pressing down with a spatula to extract as much juice as possible.

Add the cold water, sugar, and lime juice to the pitcher. Stir well until the sugar is dissolved.

Taste the agua fresca and adjust the sweetness if needed by adding more sugar.

Serve over ice cubes in glasses, and garnish with fresh mint leaves if desired.