In small bowl, whisk sauce and set aside. In another small bowl, mix chicken, soy sauce, vinegar and ginger. Set them aside.
In nonstick skillet, heat 1/2 tablespoon oil over medium-high heat. Add carrot and green pepper, stir-frying for 3 minutes. Add snow peas and stir-fry another 2 minutes. Remove vegetables from pan and set aside.
Add remaining oil to pan. Add marinated chicken. Stir-fry constantly until chicken is cooked, about 3 minutes. Return vegetables to pan.
Add onion and stir-fry for 1 minute. Add pineapple. Stir sauce and pour over mixture. Stir-fry until sauce thickens, about 1-2 minutes.