In bowl, combine broccoli, carrots, and enough boiling water to cover. Let stand 3 minutes. Drain vegetables well.
Drain juice from pineapple, reserving 1/3 cup. Set chunks aside. In small bowl, stir together pineapple juice, ketchup, cornstarch, sugar, teriyaki sauce, and garlic.
In large nonstick skillet, heat oil over medium-high heat. Add chicken and red pepper; stir-fry until chicken browns, about 4 minutes. Stir in carrots and broccoli; cook 2 minutes.
Restir pineapple-juice mixture, and pour into skillet. Cook 1 minute. Add pineapple chunks. Stir-fry 3 minutes or until vegetables are crisp-tender.