If your ideal burger is dressed with sardines and kimchi, you’re out of luck at Big Billy’s Burger Joint. But if you can combine the North Charleston restaurant’s existing patties and toppings to create the perfect sandwich, there may be $250 in it for you. Big Billy’s this month started choosing a weekly winner in its “Build a Burger” contest, which runs through Sept. 6. The top finisher will receive a $250 prize and the priceless honor of having his or her creation added to the specials menu. The dozens of ingredients available for burger construction include sliced mushrooms, ham, chow chow, queso and honey horseradish sauce. The second week’s winner garnished his burger with roasted red pepper, fried pickles, caramelized red onions and mac-n-cheese. To play, ask a Big Billy’s server for an entry form.