There are many anti-sickness meds available OTC. Personally I avoid them if possible, as they make me drowsy for a long time. But they are very effective, so you have to decide whether the ongoing drowsiness is worth it.
I've had mixed results from the wrist bands. They certainly don't do any harm. Even if the effect is psychosomatic it is worth while.
Things that help me and my dc:
Never travelling either hungry or thirsty or over-full, but somewhere in the middle. Have a sports bottle of water and some crackers or bland biscuits available in the car to stave off any hunger or thirst. Only ever sip or nibble at them.
Have the windows open if you can.
Keep the car cool. Better to be chilly and add a blanket than to be toasty warm.
Look outside of the car as much as possible. Keep your eyes focused at a distance if you can. Think about what's outside the car to encourage distraction.
Play games: I-Spy, Journey Cribbage, I Went To, Fizz-Buzz, turn-taking stories, etc.
Listen to engaging audio books.
At the least hint of nausea, SING. If you need help, have a Singing Playlist that you can sing along to. Feeling sick, and worrying about feeling sick, make you hyperventilate, which makes you more likely to feel ill and be sick. Singing regulates the breathing and prevents hyperventilation. And lifts your mood.
Take regular breaks from the car. Get out and move about. Have something light to eat and drink. Wee.