Preheat oven to 350. Prepare a 13"x 9" casserole dish with cooking spray; set aside. In a large pot, cook chicken, bell peppers, and onions over medium-high heat until chicken is no longer pink. Add spaghetti sauce, salt, black pepper, macaroni, and water. Cook until macaroni is done. Place mixture into prepared dish. Bake, covered, for 25 minutes. Remove from the oven and top with cheese. Return to the oven and bake, uncovered, for 15 more minutes, or until thoroughly heated and the cheese has melted.