Marinate the pork: In a bowl, combine the sliced pork with 1 tbsp soy sauce, 1 tbsp hoisin sauce, and 1 tsp sesame oil. Mix well and let it marinate for 10 minutes.

Prepare the sauce: In a small bowl, mix 2 tbsp soy sauce, 1 tbsp hoisin sauce, 1 tbsp rice vinegar, and 1 tbsp brown sugar. Set aside.

Stir-fry the pork: Heat 1 tbsp vegetable oil in a large wok or skillet over high heat. Add the marinated pork and stir-fry for 3-4 minutes until browned. Remove and set aside.

Cook the vegetables: In the same wok, add another 1 tbsp vegetable oil. Stir-fry the garlic and ginger for 30 seconds until fragrant. Add the bell peppers and onion, stir-frying for 2-3 minutes until slightly softened.

Combine ingredients: Return the pork to the wok. Add the pineapple chunks and pour the prepared sauce over everything. Stir-fry for another 2 minutes until everything is well-coated and heated through.

Garnish and serve: Sprinkle with chopped green onions and sesame seeds. Serve hot over steamed rice.