In a medium-sized saucepan, combine all BBQ sauce ingredients. Cook over medium heat until it starts bubbling, then reduce to simmer. It will thicken into a barbecue sauce consistency - then you can turn off the heat.
Put pork and onion in a bowl; drizzle with olive oil and sprinkle with salt and pepper to season; stir until all is coated.
Assemble skewers: alternating pineapple, red onion then grilled pork. Each skewer will have approximately two large pieces of each.
Grill all until done, turning (carefully) several times to make sure everything gets browned. Before removing from the grill, cut open one of the larger pieces of pork to make sure there's no pink remaining inside.