Preheat A Grill For Medium Heat. When Hot, Lightly Oil The Grate. In A Medium Bowl, Lightly Mix Together The Ground Beef, Barbeque Sauce And Garlic Powder. Separate Into 4 Portions And Flatten Into Patties. Grill The Burgers For About 8 Minutes Per Side, Or Until Well Done. Place A Slice Of Cheese On Top Of Each Burger And Allow It To Melt For A Minute. Press Chopped Cilantro Into The Melted Cheese On Each Burger. Serve Burgers On Toasted Sourdough Bread Topped With Lettuce And Tomato. Feel Free To Use Other Condiments To Your Liking.