Pulled Pork Sandwich

Pork shoulder roast, about 4 pounds (I buy the big one from Costco or Sam's, it is shaped as a roll)
1 1/2 c water (estimate)
1-2 bottles (16 oz) BBQ sauce (I use the Famous Dave's Rich and Sassy)
1 bottle brown sugar BBQ sauce
Brown sugar to taste
Chopped Onion (optional)

Add pork and water, cover and cook on LOW for 8-10 hours or 4-5 hours on HIGH heat setting (I cook it overnight in a roaster). chop the meat coarsely and discard excess fat. Put the pork back in the slow cooker. Add BBQ sauce and chopped onion (optional) and brown sugar. Cover and cook on LOW for 4-6 hours longer. Stir occasionally.