Cut the beef and vegetables into bite-sized pieces.
In a bowl, make the marinade by mixing soy sauce, sugar, sesame oil, and minced garlic.
Add the marinade to the beef and let it sit for about 10 minutes.
Add cooking oil to a pan and stir-fry the beef over medium heat.
Add the vegetables and stir-fry together until cooked.
Finish by sprinkling sesame seeds and black pepper on top.