A clothing retailer was scheduled for approved AC repairs at the Newpark Mall in Newark CA. While cleaning the inside coil, our technician found a Styrofoam cup had broken up, and crumbled pieces adhering to the evaporator coil. Turned unit off so that most of the Styrofoam would fall off. Used a pole brush and evap coil cleaner to clean off remaining debris, vacuumed up the smaller bits that had fallen. After cleaning, turned unit back on and cycled to test. Unit running well now, job complete.