Turn instant pot onto "saute" function.
Once instant pot is heated up, add oil and chicken. Season with salt & pepper, to taste. Lightly brown chicken on one side and turn over to lightly brown on other side. (You don't need to cook chicken through.) Add garlic and cook one additional minute.
Add vinegar, brown sugar, ketchup, soy sauce, pineapple and juice, chopped bell peppers and a little red pepper flakes (if desired). Stir all together.
Place lid on the instant pot and lock into place. Place knob on back of unit to "Sealing".
Cancel "saute" function and press manual or pressure cooker button. Set for 10 minutes. After 10 minutes are done, do a quick release, wait for pin to drop and safely remove lid away from you.
Place instant pot onto "saute" mode. Mix together cornstarch and water to make a slurry and pour over chicken and stir well until mixture is thick.
Serve over your favorite cooked rice is desired.
