oh my yes. you can pack just about anything but glass (perhaps aluminum cans are a no-no too, i am not sure) in your backpack for snacks (or even lunch) and be just fine.
they say no outside food is permitted in the parks, but i have never seen that enforced.
We always bring along goldfish, individual snack packs of cookies, frut snacks and such. Heck, we have been known to bring in sleeves of saltines and a can of spray cheese, uncrustable
PB&J sammies and turkey wraps. All of this went thru the security check with nothing said. Of course this was all in our backpacks. But i have seen some folks bring food or baby needs thru in a small soft sided cooler. They are pretty OK with reasonable things such as this.
I wouldn't try to go trucking thru the gates with a whole ham, bucket of KFC, and a full watermellon for your own personal pick-nic, but light snack/lunch stuff will not be an issue.
the one time we tried to bring in Snapple in glass jars though, we were stopped, informed about the no glass thing and given the opertunity to stand off to the side and pour our Snapple from the glass jars to our then empty refillable mugs.
- lori