Break the Seal, Buy the Contents
Ok, all due sympathy to modern parents who can no longer resort to corporal punishment, but that doesn't mean they don't have to answer for the bad behavior of their scions. A toddler marching down an aisle brazenly ripping open a bag of chips and stuffing her face with it, or somehow bypassing the safety seal on a bottle of chocolate milk and chugging the contents, cannot be allowed to walk away from her crimes scot-free. Or, at least, her parents can't. Somebody's got to pay.
The subtler the offense, the more likely a caregiver is to try to disguise what happened. "I can re-wrap this chocolate bar, place it carefully back on the shelf and nobody will be the wiser," goes the thinking. Or, "A few finger holes in cellophane don't count. Those mushrooms could use more ventilation." This is slippery-slope thinking. Where does it stop?
No, whether you're an adult or an ankle-biter, if you open something, you must pay.