Sweet and Sour Chicken is a great dish to freeze, it remains very delicious after thawing.  Just let the stir-fry cool completely before freezing and then transfer to a freezer bag or airtight glass container (freezer-safe). Thaw in the fridge or room temperature and reheat in the skillet over the stovetop.  However, on this note, pineapple may not retain the same flavor and texture after thawing. If you add pineapples here, prepare as much as you will consume or remove the chunks before thawing and add fresh ones when reheating.