In a large bowl, season the fresh pork spare ribs with salt and black pepper until evenly coated. Extract juice from grated ginger by squeezing it through a strainer and set aside. Combine pineapple juice from the canned pineapples, soy sauce, banana ketchup, and the ginger juice in a bowl. Add the seasoned spare ribs to this marinade and gently massage the liquid into the meat. Place in the refrigerator for 30 minutes.

Remove the meat from the marinade and drain well, saving the marinade for later. Heat oil in a deep pot over medium heat. Cook chopped onions and minced garlic until the onions become soft and clear, about 3-4 minutes. Add the marinated spare ribs and cook, turning occasionally, until the meat browns lightly on all sides, about 8-10 minutes.

Pour in the saved marinade and water, then bring everything to a boil. Once boiling, lower the heat, cover the pot, and let it simmer gently for 40-50 minutes. Stir occasionally to prevent sticking. You'll know the meat is ready when it's tender enough to easily pull apart with a fork.

When the meat is tender and the sauce has thickened slightly, add the pineapple chunks. Cook for 2-3 minutes more until the pineapples are heated through. Taste the sauce and add more salt or pepper if needed. Turn off the heat and let everything rest for 5 minutes before serving.

For best results, serve hot over steamed white rice. The sauce should be thick enough to coat the back of a spoon, and the meat should easily separate from the bone. Any leftovers can be stored in an airtight container in the refrigerator for up to 3 days.