I need to write a sign for volunteers not to give food for free as polite as I can?

We conduct a festivel for our church in CA to support us. We do get a lot of volunteer to put this hugh event. However, we have noticed the volunteers that do the cooking e.g. Gyro or Sovlaki are giving some for free to people they know. I need to put a sign that needs to be posted thru out the kitchen area for volunteer to not give food away. How can I write something that will not insult them? I am looking for somthing simple and to the point. Thanks for all feedback