Place the chopped onions in the bottom of the slow cooker. Place the pork on top of the onions. Add garlic, ground mustard, cayenne pepper, salt, pepper, cider vinegar and Worcestershire sauce. Pour the Dr. Pepper on top and cook high 4-5 hours or low 8 hours.

Carefully remove meat and place on cutting board. Using two forks shred the pork by pulling away from each other. Place the pork back into the slow cooker for 1 hour.

Drain the remaining juices and toss the meat and onion mixture in BBQ sauce of choice. Add BBQ sauce until you reach your desired level of sauciness.

Top onto buns and enjoy. Great with slaw and oven fries.