I'm currently flying a Pacific trip and had a fellow crew member give me a few packs of this Energy Gel called GU. It packs way better than Power bars and provides the energy boost you need after a long flight (and before decent). I flew back from HNL to NRT yesterday and took one of these things before starting the decent - I DID feel much better & not as tired as I normally do after this leg. Amazon is selling a case for $19, I just ordered 2 cases. These will be great to throw in the flight bag for a quick pick me up.

GU Energy Gel