Combine 2 cups water and sugar in a small saucepan. Cook over medium heat, stirring frequently, until sugar dissolves and mixture comes to a boil; boil 5 minutes. Set aside.
Place tea bags in a 1-quart glass pitcher; slowly pour boiling water over tea bags. Cover and steep 15 minutes. Discard tea bags. Combine tea, reserved syrup, remaining water, and orange and lemon juice; stir until well blended. Chill.
Serve chilled tea over ice; garnish with lemon slices.