Preheat your oven to 350°F (175°C). Line a baking sheet with aluminum foil and lightly grease it, or use a loaf pan.

In a large bowl, mix together the ground beef, breadcrumbs, milk, beaten egg, chopped onion, minced garlic, Worcestershire sauce, salt, and pepper until well combined. Avoid overmixing to prevent the meatloaf from becoming tough.

Fold in the shredded cheddar cheese into the mixture, or create a layer of cheese in the middle of the meatloaf by forming half the meat mixture into a loaf shape, adding a layer of cheese, then topping with the remaining meat mixture.

Transfer the meat mixture to the prepared baking sheet and shape it into a loaf, or press the mixture into the prepared loaf pan.

In a small bowl, mix together the ketchup, mustard, brown sugar, and apple cider vinegar (if using) until well combined.

Spread half of the glaze over the top of the meatloaf before baking.

Bake in the preheated oven for about 1 hour or until the meatloaf reaches an internal temperature of 160°F (71°C). Halfway through the baking time, spread the remaining glaze over the meatloaf.

Let the meatloaf rest for 10 minutes after taking it out of the oven. This rest time allows the juices to redistribute.

Slice and serve hot.