Not to stray too far from the best topic ever, that being coffee but as an addition to it. If you're going to carry some teabags, peppermint tea is a real nice idea if you're prone to any sort of congestion or sore throat issues. It's also good for the digestion.

I always bring some with me because as much as it pains me to admit, coffee can't cure every ill.

Excuse me, gotta go get a refill now...