Soak wooden skewers in water for at least 20 minutes to prevent burning.
In a small mixing bowl, whisk together the coconut aminos, tomato paste, apple cider vinegar, garlic powder, smoked paprika, and honey to create the barbecue glaze.
Cut the top sirloin into 1-inch cubes and toss them in a bowl with the avocado oil, sea salt, and black pepper.
Prepare the vegetables and pineapple by cutting them into uniform 1-inch pieces.
Thread the steak, pineapple, bell pepper, and red onion onto the skewers, alternating the ingredients until the skewers are full.
Preheat a grill or a cast-iron grill pan over medium-high heat.
Place the skewers on the grill and cook for 3-4 minutes per side.
During the final 2 minutes of grilling, brush the skewers generously with the barbecue glaze on all sides until the sauce is bubbly and slightly charred.
Remove from the heat and let the beef rest for 2 minutes before serving.