Slice the beef thinly.
Julienne the bell pepper and onion.
In a bowl, mix soy sauce, sugar, minced garlic, sesame oil, and pepper to make bulgogi marinade.
Marinate the beef with the sauce for 20 minutes.
Stir-fry the beef and vegetables in a pan.
Cut the pita bread in half to make a pocket.
Fill the pita bread with bulgogi and vegetables.
Add any desired vegetables to finish.