Food and beverages are a very personal choice. I ride with a camelback and usually use grape propel in it. For me a good breakfast is very important, it's the main fuel for the race. I like a bunch of scrambled eggs for the protein. Banana and some whole wheat toast. Then a couple more bananas before the race and usually mixed nuts and/or a protein bar or Lara bar. I have hand/wrist issues so I always take aleve to help with that.
Take a cooler with cold water and something to eat after the Race, I promise you will be starving.
If you get arm pump stop for a few seconds and shake them out, for me I would rather lose a little time shaking them out then pushing through and piling up Into a tree or taking someone else out. A little time lost here and there does add up but crashing a bunch because you can't feel the levers wastes more time and energy.