Breathe. Take a few deep breaths. Recline your seat and close your eyes. If worse comes to worse, fake motion sickness and have them pull over in s place where you can get some water and compose yourself until the meds kick in.
Need something funny? We were stuck in traffic this weekend in Chicago. My 3 year old pipes up from the back: "Umm, excuse me, Daddy? Can you please honk your horn and ask these people to move out of our way?" When we told him that's not how it works, he said, "Oh, come on, Dad! You can do it! Just try! The horn is REALLY loud!"
Need something calming? You will get through this. Deep breaths. Can you share about your favorite vacation memory/destination?