I used to suffer really badly with travel sickness, before a trip I once tried Nelsons Travella which is a homeopathic remedy which I found really helpful. Here is the link http://www.nelsonsnaturalworld.com/en-gb/uk/a-z-of-ailments/travel/travel-sickness/#naturalremedies
I also have read that Ginger can be helpful some people even suggest the crystalised ginger to eat as a sweet although I prefer the fresh root which can be drank in tea you could add honey to sweeten the taste. Or you could also use ginger aromatherapy oil which can be inhaled.
Hope this is of some help