Place the pork cubes, diced onion, and bell pepper chunks into the slow cooker.
Drain the pineapple chunks and set them aside. Pour the juice into a mixing bowl.
Add the ketchup, rice vinegar, brown sugar, soy sauce, and minced garlic to the pineapple juice. Stir until the brown sugar dissolves.
Pour the sauce over the pork and vegetables in the slow cooker. Add the reserved pineapple chunks and stir to coat everything evenly.
Cover and cook on low for 6 to 7 hours until the pork is tender.
In a small bowl, mix the cornstarch with 2 tablespoons of cold water. Stir this slurry into the slow cooker during the last 30 minutes of cooking to thicken the sauce.
Serve the pork and sauce over cooked white rice.