Cook rice according to package directions.
In a large skillet over medium-high heat, brown the ground beef until fully cooked. Drain excess grease if needed.
Add minced garlic and cook for 30 seconds.
Stir in brown sugar, soy sauce, sesame oil, ginger, black pepper, and red pepper flakes if using.
Simmer for 2 to 4 minutes, stirring often, until the sauce thickens slightly and coats the beef.
Stir together mayonnaise, sriracha, and rice vinegar or lime juice in a small bowl.
Serve the beef over rice with toppings and drizzle with sriracha mayo.
