In a large skillet, cook bacon over medium-high, stirring occasionally, until fat is rendered and bacon is lightly browned, about 20 minutes. With a slotted spoon, transfer bacon to paper towels to drain. Pour off all but 1 tablespoon fat from skillet; add onions and garlic, and cook until onions are translucent, about 6 minutes.
Add vinegar, brown sugar, maple syrup, coffee, whisky and smoked paprika and bring to a boil, stirring and scraping up browned bits from skillet with a wooden spoon, about 2 minutes. Add bacon and stir to combine.
Transfer mixture to a slow cooker and cook on high, uncovered, until liquid is syrupy, 4 1/2 to 5 hours. Transfer to a food processor; pulse until coarsely chopped.
Let cool, then store in airtight containers and refrigerate or freeze.