We usually just take nuts (mostly raw almonds & walnuts - occasionally pecans) and dried fruit (dates, raisins, a few cranberries, apricots & sometimes prunes).
Occasionally, I'll throw in a few pretzels or crackers...maybe some Cheerios if we're low on other things.
I rarely take fresh fruit or veggie sticks, because I just stuff everything in a Zip-Loc and don't want to worry about things going bad. If I do take fruits and veggies, it's usually apple wedges, carrot sticks or baby carrots, sugar snap peas, celery, grapes or grape tomatoes - just one or two of those at a time.
The kids have a water bottle of their own, with a sippy cup type lid, so I just make sure to fill that whenever we go out.
ETA: I take granola bars, if I've got a batch in the house. I don't buy any of the commercial ones, but do make my own sometimes.