If using wooden skewers, soak them in water for at least 30 minutes before grilling.
Cut pork tenderloin into even 1-inch cubes. Cut pineapple into 1-inch chunks. Cut red onion and green bell pepper into 1-inch pieces.
In a small bowl, whisk together BBQ sauce, olive oil, soy sauce, garlic powder, and black pepper until fully combined.
Place pork, pineapple, red onion, and bell pepper into a large bowl. Pour the BBQ marinade over everything and toss until all pieces are evenly coated.
Thread the marinated pork, pineapple, onion, and bell pepper onto skewers, alternating ingredients. Leave a small space between each piece for even cooking.
Preheat grill to medium heat.
Place skewers on the grill and cook for 15 to 20 minutes, turning every 3 to 4 minutes to ensure even cooking on all sides.
In the last 2 to 3 minutes of grilling, brush skewers with additional BBQ sauce for a sticky glaze.
Remove skewers from grill when pork reaches an internal temperature of 145°F (63°C).
Let rest for 1 to 2 minutes before serving.
