In a large saucepan, combine the sugar and water. Heat over medium-high heat, stirring until the sugar has dissolved. Bring the mixture to a boil, then remove from heat and allow it to cool for about 5 minutes.

Transfer the sugar water to a large pitcher. Stir in the mint-flavored syrup, lemonade concentrate, and limeade concentrate until well combined.

Place the pitcher in the refrigerator and chill until the mixture is completely cooled, approximately 30 minutes.