1.In A Large Saucepan Over Medium-Low Heat, Blend Reserved Pineapple Juice, Soy Sauce, Vinegar, And Brown Sugar. Mix In Flour, And Stir Until Thickened. 2.Stir Bell Peppers, Celery, And Water Chestnuts Into The Saucepan. Mix In Chicken. Cook And Stir Until Heated Through. Stir In The Pineapple Chunks Before Serving.