Cook and stir bacon in a large saucepan over medium-high heat until bacon starts to brown, about 10 minutes; drain grease, retaining 1/4 of the drippings. Stir onions into bacon and drippings; cook and stir until soft, about 10 minutes. Stir in brown sugar; cook until onions are sticky and browned, about 5 more minutes. Mix in garlic, cayenne pepper, cinnamon, and nutmeg. Cook and stir until garlic is soft, about 5 minutes.

Mix in bourbon whiskey, coffee, sherry vinegar, and maple syrup. Bring to a boil, reduce heat to low, and cook until the bacon jam is thickened but not completely dry, stirring occasionally to prevent burning, about 35 minutes. Mix in ketchup and cook 5 more minutes.

Remove from heat, let the bacon jam cool, and pulse in a food processor to a slightly chunky, spreadable consistency. Bacon jam will store in the refrigerator, covered, up to 2 weeks.