Start your smoker and keep the temperature low. We’re looking for lots of smoke and the temperature around 190-200 degrees.
Season the brisket on all sides with the salt/pepper/garlic mixture (reserve 1/2 tablespoon of the seasoning for later use). Place the brisket on the grill grate, close the lid, and smoke for 3 hours.
After the brisket has smoked for 3 hours, remove to a large sheet of plastic wrap. Tightly wrap the brisket with the plastic wrap, then wrap again with foil and place in the refrigerator overnight. This step is important for well penetrated smoke flavor, but if you’re cooking same day, just skip the wrapping and go on to the next step.
The next day, preheat your grill or a cast iron grill pan to high heat (around 500 degrees). Unwrap the brisket and place it fat side up on the hottest part of your grill. Grill for 8-10 minutes per side, or until the brisket has developed a nice char on both sides.
Meanwhile, preheat a large dutch oven over high heat. Cook the bacon until golden brown and crisp. Add the diced onions to the pan and cook until tender (about 6 minutes) then add the garlic and cook an additional 2 minutes. Stir in the tomatoes, chili sauce (or ketchup), brown sugar, molasses, beef stock, and the remaining salt/pepper/garlic mixture. Bring to a simmer.
When the brisket has finished searing on both sides, nestle it into the hot bacon/onion/tomato barbecue sauce. Turn the temperature setting on the grill down or preheat your oven to 350 degrees.
Cover the dish with a lid or tin foil and place directly on the grill or in your oven. Close the grill lid and cook for 1 1/2 hours. The liquid will have decreased by about half. Pour in the beer to bring the liquid back above the brisket. Put the lid back on and return to the grill or oven for an additional 1 1/2 hours or until the brisket has reached an internal temperature of 205 degrees.
Remove the brisket from the baking dish to a cutting board and allow it to rest for at least 15 minutes. While the brisket rests, add the cider vinegar to the braising liquid and cook over medium heat. Bring the sauce to a boil and stir frequently until it is reduced to a thick BBQ Sauce consistency. You may need to separate any excess bacon fat from the top with a spoon.
Slice the brisket in 1/4 inch slices (about as thick as a pencil) and drizzle with the warm BBQ sauce. Serve immediately and enjoy!