For day hikes we don't eat much on the trail. Our hikes are typically 8-13 miles, entail 2400 feet or so elevation gain and loss, and start in the morning after breakfast. Those take 5 or 6 hours, usually.

I always have a couple of Clif MoJo Bars in my pack. On humid summer days when salt is sweating out, I pack a ziplock of chips: Doritos or Fritos. And a ziplock of some kind of salted nuts -- cashews, almonds or mixed.

And some kibble for my pup, of course. :-)

I've never backpacked overnight so have no guidance to offer in that regard.