When I taught third grade, our focus was on learning about the regions of the United States. Learning about what crops were grown in that region was always a key idea for them.
Here are some of the food ideas and the region of the United States with which it is related:
Northeast Region: Wild Blueberry muffins from Maine, Hershey Chocolate from Hershey,PA
Southeast Region: Key lime pie from Florida, peanuts from Georgia, gumbo from New Orleans
Midwest Region: Pemmican (Plains Indians), cheese from Wisconsin, corn products from Iowa
Southwest Region: Any kind of Mexican food from tacos to burritos
West Region: California fruit (oranges, grapes, raisins) pineapples from Hawaii
If you are a teacher, you might want to ask parents to volunteer to bring some of these foods into the classroom and then help serve it.
There are more food ideas. If you have any ideas, feel free to make a comment.