Preheat the oven to 350°F (175°C).

In a large skillet over medium-high heat, add ground beef and cook until fully browned, about 7–10 minutes.

Return the skillet to medium heat, add onion, green bell pepper, red bell pepper, and minced garlic. Sauté for 5–7 minutes until softened.

Stir in diced tomatoes, ketchup, brown sugar, mustard, salt, and pepper. Simmer on low heat for about 10 minutes.

Boil salted water and cook penne pasta until al dente, approximately 8–10 minutes. Add corn during the last 3 minutes.

Combine pasta and corn with the Sloppy Joe sauce in the skillet.

Spread the mixture evenly into a baking dish, top with shredded cheese, and bake for 20 minutes.

Let the casserole rest for a few minutes before serving.