Buy in bulk and separate as needed. It costs TONS more for individual snack packs, or even regular boxes/packages, than it does to buy a giant case at Sam’s Club or Costco (or other bulk foods store) and portion out. To further save on the go, get reusable snack containers, bags, or squeeze pouches, and wash between uses.
Make your own trail mix, snack bars, and even crackers if you can swing it. Way cheaper, and you know exactly what’s going in (and what’s not).
Limit snack times to certain parts of the day. We personally do two snack times, around an hour before lunch, and around an hour before dinner. This ensures everyone isn’t absolutely STARVING by dinner time (read: making your life crazy), and won’t be over-inhaling the main meal, either.