2. Heat oil in a non-stick skillet. Saute chicken until cooked through. Remove it from pan and add green pepper, onion and celery. Saute until crisp-tender. Return the cooked chicken to the vegetables in the skillet. Add the apple and heat thoroughly.
3. Combine cornstarch, apple juice, salt, pepper, soy sauce and vinegar. Add to the pan and cook until sauce thickens.