Preheat the oven to 375 degrees and line a baking sheet with parchment paper.
In a large bowl, combine the ground beef, crushed saltine crackers, diced apple, chopped sage, egg, milk, onion, salt, and pepper. Mix with your hands until the ingredients are evenly distributed.
Shape the mixture into a loaf about 8 inches long and place it on the prepared baking sheet.
In a small saucepan, stir together the bourbon, brown sugar, and ketchup. Heat over medium heat for 3 minutes until the sugar dissolves and the glaze thickens slightly.
Brush half the glaze over the meatloaf. Bake for 30 minutes, then brush with the remaining glaze.
Continue baking for another 15 to 20 minutes until the internal temperature reaches 160 degrees. Let the meatloaf rest for 5 minutes before slicing.