Sarah Matilda did this when we were on our way down Tamborine Mtn, now she does it everytime we come down the mountain (which is weird because she's fine going up...) But she will not have eaten for 2-3 hours had only water and STILL vomit up that yucky cheese smelling stuff.... I do think it is a form of car sickness and being changed around can cause it, like coming down the mountain their bodies aren't used to moving that way constantly yet. With Matilda now when we come down we put towels out around her & give her sips of water to help get her settled. No luck yet unfortunately... but she doesn't vomit at other times. :-k