In a large skillet, cook 1.5 pounds of bacon over medium-high heat until lightly browned and most fat is rendered, about 8–10 minutes. Drain excess grease, reserving about 1 tablespoon.

In the same skillet, add diced onions and smashed garlic. Sauté over medium heat until onions become translucent, about 6 minutes.

Stir in ½ cup apple cider vinegar, ½ cup packed light brown sugar, ¼ cup pure maple syrup, ½ teaspoon red pepper flakes, and ¾ cup brewed coffee. Bring to a boil for 2 minutes.

Add cooked bacon to the skillet, stirring until well combined. Transfer to a 6-quart slow cooker.

Cover slow cooker and set on HIGH, cooking uncovered for 3.5 to 4 hours, stirring occasionally.

Pulse the bacon jam in a food processor until it reaches a coarse consistency, with some chunks remaining.

Allow the bacon jam to cool to room temperature and transfer to an airtight container.