It is a common problem of NAUSEA during travelling because of motion sickness. Or sometimes it is due to Gastritis because of SPICY foods. Or sometimes it may be because if travel related stress.
The Treatment depends on what is the cause.
Occupying yourself in something dies help in relieving motion sickness.
Next Steps
avoid spicy foods coffee tea cold drinks alcohol smoking junk food etc.
have more of salads, simple food during travelling, have small quantities of food. often it is not realised that overeating is done during travelling.
Health Tips
discuss in details about your problem for accurate guidance.