In a medium bowl, mix the vinegar, garlic, honey, olive oil, ground black pepper, Worcestershire sauce, onion powder, salt, and red pepper flakes.
Place steaks in a shallow glass dish with the marinade, and turn to coat. For optimum flavor, rub the liquid into the meat. Cover, and marinate in the refrigerator for 1 to 2 days.
Preheat grill for medium-high to high heat.
Lightly oil the grill grate. Grill steaks 7 minutes per side, or to desired doneness. Discard leftover marinade.
Recipe adapted from allrecipes.com