Preheat your oven to 350°F (175°C). Line a 9x5 inch loaf pan with parchment paper for easier removal, or lightly grease it.
Mix all meatloaf ingredients. In a large bowl, combine ground beef, eggs, oats, ketchup, Worcestershire sauce (if using), garlic powder, onion powder, salt, pepper, and grated carrots (if using). Mix gently with your hands until just combined—don't overwork the meat or it'll become tough.
Form your loaf. Transfer the meat mixture to the prepared loaf pan and gently press it into an even layer. Create a slight indentation down the center (this helps the glaze pool on top).
Make the sweet and sour glaze. In a small bowl, mix together the ketchup, brown sugar, white vinegar, and honey until well combined.
Apply half the glaze. Spread half of the sweet and sour glaze over the top of the meatloaf, reserving the other half for later.
Bake initially. Place the meatloaf in the preheated oven and bake for 40 minutes.
Add the remaining glaze. After 40 minutes, remove the meatloaf from the oven and carefully drain off any excess fat (if desired). Spread the remaining glaze over the top.
Finish baking. Return the meatloaf to the oven and bake for an additional 15-20 minutes, or until the internal temperature reaches 160°F (71°C) and the glaze is caramelized.
Rest before slicing. Allow the meatloaf to rest for 10 minutes before slicing. This helps it hold together better.
Slice and serve. Cut into slices about 3/4-inch thick and serve warm. For extra kid appeal, call it "meat cake" and watch the attitude change!