In a saucepan, place the ketchup, rice wine vinegar, sugar, pineapple juice and soy sauce and bring to a simmer. Prepare a cornstarch slurry by mixing the cornstarch and sugar. Add the to sweet and sour sauce and allow to simmer for 2 minutes. Remove from heat, cover and set aside.
Sweet and Sour Pork
Place the boneless pork strips into a bowl. Mix with soy sauce, Shaoxing wine, minced garlic and cornstarch and allow to marinate for at least 30 minutes.
Mix together the flour, egg, cornstarch, salt, baking powder in a bowl. Toss the marinated pork pieces in the batter. In a wok, heat about 1 cup of oil until hot. Fry the battered pork pieces for about 4-5 minutes until the pork cooked and golden brown. Add the pork pieces one at a time, so they don't clump together as they fry. Remove and allow to drain on a paper towel on a plate. Repeat until all the pork is cooked.
To prepare the vegetables, heat 1 tablespoon fresh oil in a wok until hot and fry the onions and bell peppers and pineapple chunks for about 2 minutes. Return the crispy pork back to the wok and pour over the sweet and sour sauce. Toss to coat, serve with steamed white rice.