Drain pineapple, reserving 2 tbsp (30 mL) juice. Stir reserved pineapple juice with hoisin, soy sauce, rice wine vinegar and garlic; set aside.
Heat the oil in a wok or large sauté pan set over high heat and cook pork for 2 minutes or until just cooked through. Transfer to plate.
Add bok choy and red pepper and cook, stirring for 2 to 3 minutes or until vegetables are tender crisp. Stir in pineapple, cook for 1 minute before stirring in pineapple hoisin mixture. Bring to a boil, stir in pork and cook for 30 to 60 seconds or until heated through. Garnish with green onions and serve.
Serve with rice or rice noodles.