Combine all ingredients for rub together in a small bowl. Mix together and season brisket well. Place in crockpot on low.
Dump all ingredients for marinade in crock pot with brisket. Stir to combine.
Let cook 5-6 hours on low or until brisket is tender and shreds easily with a fork. Remove from crockpot (be sure to scoop out all the peppers and onions too!). Discard all but 2 cups of liquid.
Place brisket back in crockpot with liquid and cook for an additional 1/2 hour. Serve with desired toppings.