Sauté pork belly until crisp; remove from pan to a paper towel. Pour off all but 1 tablespoon fat from the pan. Add apples; salt and pepper to taste and sauté until golden around the edges; remove from pan to a paper towel. Add both halves of pretzel stick to pan and brown on both sides. Remove from pan and place on plate or board to build sandwich. Add BBQ sauce to both halves of bread. Add arugula, apples and pork belly to bread bottom. Cover with top half of bread, cut in half and serve.