Begin by slicing the beef sirloin into thin strips. Chop one onion and a few bell peppers into thin slices.

In a mixing bowl, combine soy sauce, sesame oil, minced garlic, and sugar to create your marinade. Add the sliced beef, making sure each piece is well-coated. Let it marinate for at least 15 minutes.

Heat a skillet over medium-high heat and add a teaspoon of oil. Toss in the chopped onion and bell peppers, sautéing for about 5 minutes.

Push the sautéed veggies to one side of the skillet and add the marinated beef to the other side. Cook for about 5 minutes until browned and cooked through.

Mix in the chopped kimchi and cook for another 2 minutes. Stir for even distribution.

Toast the hoagie rolls and fill each roll with the beef and veggie mixture. Top generously with cheese and broil for about 2 minutes until cheese is melted.