In a mixing bowl, combine the soy sauce, vinegar, brown sugar, ketchup, minced garlic, black pepper, and salt to prepare the marinade.

Add the pork cubes to the marinade, ensuring they are well coated. Marinate for at least 30 minutes or up to overnight.

Preheat your grill to medium-high heat.

If using skewers, thread the marinated pork onto them, leaving some space between pieces.

Brush the grill grates with vegetable oil to prevent sticking.

Place the skewers or pork pieces directly on the grill and grill each side for about 5-7 minutes, or until cooked through and slightly charred.

Optional: Baste the pork with leftover marinade during grilling, but avoid using it too close to the end.

Once cooked, remove the pork from the grill and let it rest for a few minutes before serving.