My favorites on day hikes:
Canned sardines (in oil, for the extra calories), with a fresh flour tortilla. Bring salt, too.
Peanut butter and jelly sandwich.
Fruit: banana, orange, juicy peach. I've found with AMS when I have no appetite, a fruit can be eaten, while those other things are like cardboard in my mouth.
Granola bars. I have several favorites, and I'll take at least 4 for a day hike.
Candy: shot blocks, everlasting gobstoppers.
Trail mix: I like almonds and pecans, and those giant raisins from Trader Joes.
When climbing Whitney, eat often, and sooner rather than later. As you ascend, your appetite may disappear as altitude issues set in, so eating before this occurs is best.
Drink: At least a pint an hour for serious hiking/climbing. I bring lemonade or Koolaid mix for the added sugar. Add one or two of those electrolyte tablets you buy in the tubes. They make the drink taste sooo good -- like a lemonade soda!
