Whisk together the pineapple juice, vinegar, ketchup, salt, and brown sugar and set aside. Cook onions in a hot frying pan with olive oil. Pour a small amount of water to the pan to create steam. Stir constantly. When onions are almost translucent, put into a large bowl.
Then stir-fry peppers and transfer to bowl when softened. You can stir-fry the pineapple a little if you want too, and put in bowl when seared.
Then add meat to pan along with a little oil. Cook until meat is browned and almost cooked through. Then, add ginger.
Add juice mixture to meat and cook until sauce is thick. (You can thicken with cornstarch if you'd like). Add a little soy sauce to the mixture to taste.
Stir all ingredients together to coat with sauce and then serve over rice.