In a large saucepan, boil 2 cups of water and the sugar.
Remove from the heat and add the tea bags.
Steep for 8 minutes and then discard the bags.
Add the remaining 2 cups of water.
Transfer to a pitcher and chill.
Add the mint and crush with a wooden spoon until fragrant.
Stir in the remaining ingredients.
Serve in tall glasses filled with ice.
Garnish each glass with a mint sprig.