Combine all ingredients for the BBQ sauce in a small saucepan. Place in over medium heat and bring to a simmer. Stir occasionally for 5-7 minutes or until the sauce thickens up. Remove from heat.
To make the burgers put the ground beef, brown sugar, BBQ seasoning, Worcestershire sauce, Montreal seasoning, and BBQ sauce in a bowl. Mix together with your hands and form into 8 sliders.
Place the sliders on a grill heated to medium high heat. Cook for 3-5 minutes per side or until desired temperature is reached. Place a slice of Havarti cheese on each slider and close the lid for 1 minute or until melted.
Remove from grill and place the sliders on the buns. Top with bacon and a lettuce leaf. Slather with the bourbon BBQ sauce and serve.