Cut steak into a small bite sized pieces and place in a medium sized bowl
In a second bowl combine teriyaki sauce, soy sauce, apple cider vinegar, garlic and black pepper in a bowl and whisk it together to make the marinade
Pour the marinade over the steak and then toss to coat. Cover bowl tightly with plastic wrap or foil and refrigerate for 4-6 hours
Heat a heavy skillet, like cast iron, over medium high heat until very hot. Cook steak 3-5 minutes turning once halfway through. Discard any remaining marinade
Transfer prepared Teriyaki Steak Bites to a plate or platter and garnish with sesame seeds and scallions if desired.
*don’t crowd the skillet cook the steak in two or three batches see comments in above post