Anything more specific?
sudden changes in blood glucose level used to make me feel tired, woozy and generally unwell - actually there are lots of symptoms that would overlap with car sickness, though personally I've never had car or sea sickness, I'm pretty sure there is a genetic element there.. I also think there is a massive overlap with some of the feelings of being a bit tipsy (alcohol mainly being fermented sugar, so there is a surprising overlap there) - and clearly balance is affected by alcohol..
That is an interesting question...
Is there a pattern of change in your blood glucose that you can see repeating?