1. Coat a wok or large nonstick skillet with cooking spray; add oil. Heat at medium-high (375°) for 2 minutes. Add peas, bell pepper, and water chestnuts; stir-fry 3 to 5 minutes or until crisp-tender.
2. Combine water and next 5 ingredients; pour over vegetable mixture. Cook, stirring constantly, 1 minute or until thickened. Transfer to a bowl; sprinkle with sesame seeds. Serve immediately.