Rub the brisket generously with the coffee rub. Wrap tightly in plastic wrap and refrigerate overnight.
Prepare Pickled Red Onions: In a saucepan, combine apple cider vinegar, water, sugar, and salt. Bring to a boil, then pour over sliced red onion. Let cool and pickle for at least 30 minutes.
Prepare Chipotle Aioli: In a small bowl, combine mayonnaise, minced chipotle peppers, and lime juice. Mix well.
Smoke the brisket at 225°F (107°C) for 6-8 hours, or until it reaches an internal temperature of 203°F (95°C).
Let the brisket rest for at least 30 minutes before shredding.
Shred the brisket with two forks.
Assemble sliders by placing a portion of the shredded brisket on each brioche slider bun. Top with pickled red onions and a generous dollop of chipotle aioli.
