After reading through this, there are really so many excellent suggestions! A paper bag with biltong or jerky is hard to beat- sitting on the seat next to you while driving- bet you can't eat one!
I always liked real deal tamales with SW style red chile and pork in corn husk. Used to buy them by the dozen from local ladies who really knew how to make them! You had to order/reserve well in advance as the good ones were always in demand. Wrap a couple in foil along with a small amount of red sauce, heat on engine manifold. Same for red chile and pork burritos- wrap in foil, heat on manifold.