A family of 5 striving to reduce the amount of plastics we use, whenever we travel--be it a cross country flight or a quick drive--we pack what we consider essentials to avoid over-priced, over-packaged, over-processed products!
Using my own containers, I hit up the bulk bins to get my kids favorite snacks. I also take the time to make snacks that are more filling like granola bars and depending on the time we're leaving we'll pack a (cooler with) lunch or dinner to be eaten on the plane or at a rest stop! Along with the snacks, we take as many reusable water bottles that we can. If we're driving, we fill them up... if we're flying we wait until we get through security and fill them up at the water fountains (or get water from a soda fountain).
Not having to purchase food or drinks at the airport or at gas stations saves us from using single use disposable plastics AND lots of $$ :)