In a large saucepan, bring 2 cups of water and 1/4 cup of sugar to a boil, turn off heat then stir until sugar dissolves. Add tea bags and 8 mint leaves. Steep for 5-8 minutes. Taste for desired sweetness, add more sugar if needed. Discard tea bags and leaves. Cool. Fill 4 glasses to the brim with ice. Add the tea and garnish with mint leaves and orange slice.