Prepare the Marinade: In a large mixing bowl, combine soy sauce, sesame oil, sugar, minced garlic, grated ginger, rice vinegar, and gochujang (if using). Mix well to dissolve the sugar and blend the flavors.
Marinate the Beef: Add the thinly sliced beef to the marinade, making sure each piece is coated. Let it marinate for at least 15 minutes. For the best flavor, marinate for 30 minutes to 1 hour if you have the time.
Cook the Beef: Heat a frying pan or grill pan over medium-high heat. Once hot, add the marinated beef and cook for 3-4 minutes, stirring occasionally, until the beef is fully cooked and slightly caramelized.
Assemble the Bulgogi Bowl: In bowls, serve the cooked rice as the base. Top with the cooked bulgogi beef, julienned carrots, cucumber slices, and green onions. Optionally, add a fried egg on top.
Garnish: Sprinkle with sesame seeds and serve with pickled vegetables for extra flavor.