Wash hands with warm, soapy water for 20 seconds.
In a large skillet, combine pork, black pepper, onion, garlic, and water. Heat until pork begins to thaw.
Add in barbecue sauce and cider vinegar.
Bring to a boil. Reduce heat and let simmer until water is gone and pork is heated through. The sauce should be thick. If not, cook for a few more minutes until sauce reaches desired thickness.
Divide pork between 4 buns.