Preheat the oven to 425 degrees. Line a baking sheet with parchment paper.
Toss the sweet potato fries with olive oil, paprika, salt, and pepper. Spread them in a single layer on the baking sheet and bake for 25 to 30 minutes, flipping halfway through.
While the fries bake, heat a large skillet over medium heat. Add the ground beef and cook until browned, breaking it up with a spoon.
Add the onion and garlic to the skillet. Cook for 3 to 4 minutes until the onion softens.
Stir in the tomato sauce, Worcestershire sauce, brown sugar, salt, and pepper. Simmer for 8 to 10 minutes until the mixture thickens.
Toast the brioche buns lightly if desired. Spoon the beef mixture onto the bottom halves of the buns and add the tops.
Serve the sandwiches with the sweet potato fries on the side.