Wayback Burgers’ latest offer, the Crispy Chicken Sriracha Sandwich, doesn't just have sriracha between the buns. It has sriracha in the buns. Could this be a thing? Burger King’s A.1. Halloween Whopper has a black bun infused with A.1. Sauce. Will burger chains (and suppliers) get drawn in by the temptation to turn other sauces into bun flavorings?