Cut pork into 1 1/2" (4 cm) squares. In a medium bowl, rub pork chunks, salt and Sake together. Let sit for 10 minutes.
Cut vegetables into wedges. Cut pineapples into bite size pieces.
Heat deep-frying oil at medium heat. Deep-fry vegetables, not pineapples, for 15 to 30 seconds until mostly cooked through, one kind at a time. Coat pork lightly with potato starch. Deep-fry meat for a few minutes until golden brown. Set aside.
Mix all the sauce ingredients in a bowl, and cook in a wok or frying-pan, When the sauce is bubbling and thickened, add cooked meat and vegetables. Stir for a couple of minutes. Add pineapple at the end. Serve immediately.
