Marinate the bulgogi with soy sauce, sugar, minced garlic, and sesame oil for 10 minutes.
Wash and slice the arugula and apple.
Heat cooking oil in a pan and stir-fry the marinated bulgogi over medium heat.
Cut the bread in half and lightly toast it if desired.
Place the bulgogi on one slice of bread, then layer apple slices and arugula on top.
Cover with the other slice of bread to complete the sandwich.