Food Tray is an object used as a dish in Prison Architect.
When the Eat Regime is active (or just before), a Cook will put clean Food Trays on a Serving Table in a Canteen, along with food. Prisoners will take one Food Tray, along with Cooked Ingredients. When they have finished, they will leave a Dirty Food Tray, which will be washed in a Sink by a Cook to reuse.
Food Trays cannot be bought or sold, only Dumped. The amount of Food Trays is controlled automatically: if there is not enough of them, more will be bought. Sometimes their amount goes beyond prisoner capacity.