1. Cut the chicken breast into bite size pieces.
2. Chop the carrots, celery, red bell pepper and onions; mince the garlic, set aside.
3. In a small bowl mix water and cornstarch, set aside.
4 In a bowl combine chicken with sugar and soy sauce, and marinate the chicken well for 10 minutes.
5. In the wok pour oil and saute the garlic on medium high heat, add the chicken and stir fry for 2 minutes or until the chicken is done.
6. Add the vegetables and stir fry for 1 minute, pour the sweet and sour sauce and continue to stir.
7. Add the cornstarch and cook until the sauce has thickened.
8. Serve the sweet and sour chicken with steamed rice.