Sprinkle ribs lightly with pepper, place in crockpot, and brush with 1/3 cup of teriyaki sauce generously to ensure that the ribs are coated on both sides with sauce.
Cover with the lid and turn on low for 7-8 hours or high for 4-5 hours. Internal temperature should be 145ºF.
Remove from crockpot, cover with foil, and allow to rest for 10 minutes.
While the ribs are resting, add vinegar, garlic, and remaining 1/3 cup of teriyaki sauce to the juices in the bottom of the crockpot. For a really rich sauce, add 1/3 cup of your favorite BBQ sauce. Turn crockpot to high setting and allow to simmer until thickened, about 5-10 minutes.
Brush thickened sauce from crockpot onto the ribs, and serve warm.