In a large pot, bring 2 cups water, salt, sugar, and cinnamon stick to a boil. Stir until the salt and sugar are dissolved. Remove from heat and cool slightly. Stir in the tea, lemonade concentrate, ice cubes, and lemon slices. Allow brine to cool.
Pour brine in a large bowl, add the chicken and soak for 20 minutes while you prepare the grill.
Remove chicken from brine. Pat dry with paper towels, season with black pepper {you don’t need salt with brine!}. Grill the chicken for 5-6 minutes per side, until internal temperature reaches 160 F.