Combine the sugar, mint leaves and 3 cups pineapple chunks in a pitcher. Muddle with a wooden spoon until the sugar is dissolved and the pineapple is crushed. Stir in the remaining pineapple and the cachaca and refrigerate until cold, at least 30 minutes or up to 4 hours.
Add 6 cups ice to the pitcher and stir vigorously. Divide among glasses and garnish with mint sprigs.