Dice celery and green onion. Cut red and green pepper, and white onion into 1" cubes.
Cut pork into 1" x ¼" slices, removing excess fat. Add pork slices to medium bowl, add 1/4 tsp. sugar, soy sauce, egg white and green onions. Mix well and marinate for 30 minutes, then add ¼ cup cornstarch, making sure to coat all the pork.
In wok, heat 1 cup of oil to medium heat. Add pork and cook 6-8 minutes or until golden brown both sides, stirring occasionally. Remove with a slotted spoon and let rest on a paper towel lined plate.
Carefully remove some excess oil from wok, until there is about ½ cup remaining. Add celery, white onion, red and green pepper, still cooking on medium heat for 6-8 minutes, or until cooked. Remove veggies and set aside.
Carefully remove excess oil from wok, until there is about 2 tbsp. remaining. Add pineapple tidbits with juice, water (only ½ cup), 2 tbsp. sugar, apple cider vinegar, ketchup, and soy sauce, bring to a boil. Mix cornstarch and cold water (only ¼ cup) and add to wok, mix until sauce thickens to desired consistency. Reserve 1 cup sauce. Add pork and veggies and mix well. Reserve 2 cups.