Add the chicken stock, water, apple cider vinegar and chicken breasts. Close/secure the lid, set release valve to SEALING and select the SOUP setting. When the soup cycle is done, release the pressure and remove the chicken breasts with tongs. Use this quick trick
to shred the chicken in 30 seconds with no mess or by pulling apart the chicken with forks. Add the shredded chicken back to the soup, salt and pepper to taste and serve.