1. In a small bowl, combine broth, soy sauce, cornstarch, and granulated sugar. Mix well. Set aside.
2. In a large nonstick skillet, cook beef over medium heat, stirring, until browned, about 4 minutes. Drain off fat; transfer beef to a plate. Wipe skillet clean with a paper towel.
3. In the same skillet, heat oil over medium heat. Add celery and onion; stir-fry for 2 minutes. Add pepper and mushrooms; stir-fry until crisp-tender, about 3 minutes. Add water chestnuts; stir-fry 1 minute longer.
4. Add broth mixture to skillet. Cook, stirring constantly until thickened, about 2 minutes. Add beef; cook until heated through, about 2 minutes. Divide rice evenly among individual serving plates. Top with beef mixture.