Preheat oven to 325 degrees F.
Mix the dry rub ingredients in small bowl. Sprinkle dry rub all over the pork roast, pressing into the pork. Cover with plastic and refrigerate for at least 2 hours.
Combine liquid ingredients and the garlic powder in a medium bowl and pour into a large Dutch oven. Place pork in the oven and tightly cover with aluminum foil then lid. Roast for 4 hours or until fork tender and shreds easily. Brush the roast with cooking liquid every hour.
Remove from oven and let stand until cool enough to handle. Shred the pork with a fork or tongs into bite size pieces.
Serve on hamburger buns topped with BBQ sauce and cole slaw.