I find when I am tired if I crunch on celery and carrots, anything that is very noisy in my head, it helps... I do this when I drive home from work because I have a 50 minute commute and at times my eyes just want to close

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Another thing that makes me tired are certain types of carbs and sweet stuff, that's usually the time when I munch on something bad at work then I am very tired for the ride home... So I try as best I can to keep away from processed/sweet carbs....
Coffee doesn't even help sometimes but cold water does for some reason. I've read if you are dehydrated this can make you tired too...
Hope these hints help... Keep us posted...