Where I work, we marinate Flank Steak (what we use for London Broil, Steak Salads, and Steak Quesadillas) in a mix of equal parts Ketchup and Honey French Salad Dressing, then add in a little Soy. You want to be careful cooking these, as the sugar will burn if you leave them over the fire to long. Flank Steak is best cooked to Medium at the most, anyway.