01 - Preheat your grill or grill pan to medium-high heat, approximately 400°F (200°C). Allow grates to become fully heated for proper searing.
02 - In a small mixing bowl, combine the finely ground coffee, brown sugar, smoked paprika, chili powder, garlic powder, onion powder, and cayenne pepper. Stir until evenly blended and no clumps remain.
03 - Divide the ground beef into 4 equal portions, roughly 6 oz each. Gently shape each portion into a patty slightly wider than the burger buns to account for shrinkage. Season both sides generously with kosher salt, black pepper, and the coffee rub mixture, pressing the seasoning gently into the meat to adhere.
04 - In a small saucepan over medium-low heat, combine the ketchup, apple cider vinegar, brown sugar, Worcestershire sauce, liquid smoke, smoked paprika, garlic powder, black pepper, and salt. Simmer for 5 to 7 minutes, stirring occasionally, until the sauce thickens and coats the back of a spoon. Remove from heat and set aside.
05 - Place the seasoned patties on the hot grill. Cook for 4 minutes on the first side without moving. Flip the patties and top each with a slice of cheddar cheese if desired. Continue grilling for 3 to 4 additional minutes for medium doneness, or adjust time to your preferred temperature. During the final minute, place the burger buns cut-side down on the grill to toast.
06 - Spread a generous layer of smoky BBQ sauce on the bottom half of each toasted bun. Layer with lettuce, a grilled coffee-rubbed patty, sliced tomato, red onion rings, pickles, and an additional drizzle of sauce. Crown with the top bun and serve immediately while hot.