COOK IT.
Fire up your grill or smoker to 400°F. If using a gas or charcoal grill, set it to a medium-high heat. In a bowl, combine the apple cider vinegar, chicken stock, ketchup, and 1 tbsp of BBQ rub. Whisk well to combine and set aside.
Season the pork shoulder with the remaining 2 tbsp of BBQ Rub on all sides, then place on the grill and sear on all sides until golden brown, about 10 minutes.
Remove the pork shoulder from the grill and place in a disposable aluminum pan. Pour the premade vinegar mixture over the pork shoulder. It should come about 1/3 to 1/2 the way up the side of the pork shoulder. Cover the top of the pan tightly with aluminum foil.
Reduce the temperature of your grill to 250°F. Place the foil pan on the grill and cook for 4-5 hours, or until the pork is tender and falling off the bone.
Remove the pork from the grill and allow to rest for 15 minutes. Drain the liquid from the pan, reserving about a cup, then shred the pork and cover with the reserved liquid.
While pork is resting, place 1 cup of BBQ sauce in a large pot and heat to simmer. Toss in 4 cups of shredded pork and mix well. Divide pork among 4 toasted pretzel buns and add additional BBQ sauce, as desired.
Dig in!