Method and apparatus to agitate a liquid are disclosed herein. An example apparatus includes a first sidewall and a second sidewall substantially parallel to the first sidewall. The example apparatus also includes a top wall coupled to the first sidewall and the second sidewall. The example apparatus further includes a bottom wall opposite the top wall and coupled to the first sidewall and the second sidewall. The bottom wall has a first side to define a cavity to hold a liquid. The example apparatus also includes a protrusion extending from the first side of the bottom wall toward the top wall.