In a saucepan over medium heat, add granulated sugar, water, and mint leaves. Bring to a boil and stir until sugar dissolves.
Lightly muddle mint leaves with a wooden spoon. Simmer for 1 minute, then remove from heat. Allow to steep until cooled, about 15-20 minutes.
Meanwhile, add pineapple juice, lemon juice, and water to a pitcher.
When cooled, pour simple syrup mixture through a sieve to remove mint leaves. Add to juice mixture and stir until well combined. Add more water as needed to achieve the desired sweetness.
Refrigerate, or serve over ice and enjoy. Optionally garnish with additional mint leaves and lemon wedges.