The rule is the only food items that may be removed from the ship are those in prepackaged sealed containers/packaging. Cookies, candy, crackers et al in their original containers/packaging. Absolutely no fresh fruit or veggies or meat and no treats from the dining room, room service or other food stations or any food wrapped in a napkin.
If you de-board after the second seating of breakfast you will notice that there is a table of food just prior to baggage claim where the policy is restated and passengers that were unaware of the rule left behind the food they were going to take off the ship. It seems like such a waste of food. It is better to know the policy before hand. Thanks for asking.
It would be better to plan a quick trip to the grocery store before you start the drive home.
You didn't ask but I will warn you, there have been many reports of ants at the port. Many cruisers have left crumbs and food in their car at the port to return and find ant colonies have taken up residence in their vehicles. If you leave food in the vehicle at port make sure they are in air tight containers and no trace of crumbs.