In small saucepan, render bacon over medium-low heat for 30 minutes, stirring occasionally. When bacon has browned, add garlic and onion; cook 20 minutes longer, stirring occasionally. Drain off fat.
Add coffee, vinegar, and brown sugar; simmer over medium heat 12 minutes or until reduced by half. Season with salt, pepper, thyme, allspice, and cayenne.
For the burgers:
Gently shape beef into four 2-inch-thick patties; cover and refrigerate.
Season patty with ⅛ teaspoon salt and a pinch of pepper. Preheat flat top griddle or cast iron skillet over medium heat. Increase heat to medium-high; coat griddle with oil. Place burger on griddle; after 30 seconds, apply even pressure with a spatula, smashing burger to about ½-inch thick. Cook for 1½ minutes or until a crust has formed; flip burger and top with cheese. Cook for 30 seconds or to desired doneness.
Toast 2 slices bread. Top 1 piece of toast with burger, Applewood Smoked Bacon Jam and second piece of toast.