Boil 4 cups of water in a pot.
Remove the pot from heat once boiling.
Add 4 tea bags to the hot water.
Steep the tea for 5-7 minutes, depending on desired strength.
Remove tea bags and stir in sugar if using.
Let the tea cool to room temperature.
Transfer the tea to a pitcher and refrigerate for at least 1 hour.
Fill glasses with ice cubes.
Pour the chilled tea over the ice.
Garnish with lemon slices and mint leaves before serving.