Bring 3 cups water to a boil in a medium saucepan; add tea bags. Boil 1 minute; remove from heat. Add mint; cover and steep 10 minutes.
Remove and discard tea bags and mint. Add 1 cup sugar, stirring until dissolved.
Pour into a 1-gal. heatproof container; add orange juice, lemon juice, and 5 cups cold water. Chill or serve over ice.