In a bowl, combine beef stock, beef suet, soy sauce, vegetable cocktail and Worcestershire sauce until smooth.
With an injection syringe, inject the flavor infusion into the brisket every 1 1/2 inches (4 cm) angling it in the direction of the meat fibers. You don’t need to use the entire amount.
Wrap the brisket in plastic wrap, place on a tray and let rest in the fridge for 12 to 20 hours.
Unwrap the brisket and let it sit at room temperature on a wire rack for 1 hour. With paper towel, sponge the excess liquid from the surface.
Meanwhile, preheat the smoker, charcoal barbecue or gas grill to between 250 and 275°F (125 and 135°C). Once the cooker temperature has been reached, add your choice of smoking wood and set up for indirect heat cooking, if necessary. Season the brisket with salt and pepper to your taste. Place on the smoker, barbecue or grill over indirect heat.
Smoke the meat for about 4hours or until the internal temperature reaches 175°F (80°C). Meanwhile, fill the spray bottle with cola and spray the brisket three or four times. To avoid a loss of smoke or variations in temperature, don’t open the lid of the barbecue or smoker more than necessary (for spraying).
Remove the meat from the smoker or barbecue and place on a tray. Increase the temperature to 275°F (135°C).
Place a large sheet of butcher paper or parchment paper on a rimmed baking sheet; pour a little cola in the middle, then place the brisket on it. Seal the paper to make a pouch.
Slide the pouch off the baking sheet onto the grill and continue cooking with indirect heat for about 4 hours until the internal temperature reaches 190°F (93°C). The thermometer should go into the brisket as if it were butter. If this is not the case, continue cooking until it does.
Remove the meat from the heat, sliding the pouch back onto the baking sheet. Let rest in the paper for about 45 minutes.
Unwrap and transfer to a cutting board. Cut brisket across the grain into thin slices.