1. In a large zip-top plastic bag or shallow plastic container, combine the vinegar, sugar, Creole sesasoning, teriyaki sauce, oregano, salt, and pepper. Seal the bag or container and shake to combine the ingredients. Add the flank steak, seal, and shake again to coat. Marinate for at least 15 minutes or as long as 3 days ahead.
2. Preheat the broiler, a stove-top grill pan, or outdoor grill, then broil or grill the steak 5 to 7 minutes per side for medium or to your desired degree of doneness. Let the steak stand 10 minutes on a serving platter before slicing crosswise into 1/2-inch thick slices.
From Robin Miller's Quick Fix Meals.