Here is the response of the doctor:
It is called motion sickness,
Always stop your child’s oral diet at least 2.5hours before starting journey , and give him 4cc syp.gravinate/ Phenergan 1 hour before starting journey .
Don’t feed before or during the journey. Phenargan is excellent to treat motion sickness and can be repeated after 6 to 8 hours. Preferably the child should be asleep during travelling.