Preheat oven to 375°F. Line a loaf pan with parchment paper.
Combine breadcrumbs and milk and let soak for several minutes.
Add ground beef, eggs, onion, garlic, ketchup, mustard, Worcestershire sauce, salt, and pepper. Mix gently until combined.
Fold in half of the shredded cheddar and any optional add-ins.
Transfer to loaf pan or shape freeform on a baking sheet. Smooth the top.
Bake for 45 minutes.
Mix ketchup, mustard, brown sugar, and vinegar to make the glaze.
Remove meatloaf from oven, spread glaze on top, sprinkle remaining cheese, and return to bake 15–20 more minutes until internal temp reaches 160°F.
Let rest for 10 minutes before slicing and serving.