First of all, water. If you have motion sickness, that can cause nausea and vomiting. By vomiting you loose a lot of water and you need to stay hidrated.
You should have some paper bags of those you can find on airplanes. Those come handy in case you are vomiting. Paper tissues are also a good thing to have.
There are certain tablets that can help. Go to the pharmacy and ask for help, they know what to give you.
There are a few things you can do before and during your travel.
Before traveling, be careful what you eat and drink. Limit your food intake, eat something light, avoid alcohol and DO NOT drink coffee!!! This is the most important step! Coffee can disturb your stomach and make you sick during traveling. I'm telling you this from experience.
Make sure you have plenty of air and take deep breaths, repeatedly. If you're traveling by car, make sure you sit on front of the car and look straight ahead. Never sit facing backwards, that's the biggest mistake you can do.
On a plane you should choose a seat in the middle of the plane or close to the wings, in case of a ship choose a place close to the middle and the lower deck if possible.
Reading or looking at your phone can be disturbing in case you are suffering from motion sickness, so you should avoid it.
Travel sickness or motion sickness is very common. I have experienced it a few times but that was many years ago now. I have learnt to become a good traveler and have a few tricks.
If I am flying on a long haul flight over 10 hours I will eat before hand and consume loads of liquids. Staying hydrated is important as the pressurized cabin and recycled air will dehydrate you twice as fast compared to being outside in fresh air.
If you are travelling by train , try and face the front as otherwise your body becomes disorientated and you could feel queezy. Try and always face the front whilst travelling.
Having bottled water on hand is important as if you drink local water in other countries your body can react by having an upset stomach. If it is even for brushing your teeth use the bottled water. Avoid ice cubes in drinks as This has struck before causing diarrhea.
Happy travelling and stay safe.