Place chicken breasts in the bottom of the pressure cooker insert.
Whisk together chicken stock, pineapple juice, ketchup, soy sauce, rice vinegar, honey and pepper. Pour over the chicken.
Place the lid on the pressure and slide it into the lock position. Set the pressure to high and cook time to 10 minutes.
Once the time has elapsed and the machine beeps to signal the end of cooking time, allow a natural release for 10 minutes, then use a kitchen utensil to open the valve to release any remaining steam. Careful, steam will be hot. Remove the chicken to rest.
Meanwhile, turn the pressure to Saute and add the chopped pepper and onion. Bring to a boil. Meanwhile, shred or chop the chicken.
Stir together the cornstarch and cold water, then add to the sauce. Stir and cook until it thickens. Add the chicken back into the sauce and cook for a few seconds to combine the flavors. Turn off the pressure cooker.
Serve the shredded sweet & sour chicken over rice. Serve hot and store leftovers in an airtight container for up to 2 days.