Dont use them, no matter what you use bleach, petrol etc the smell of the food which is impregnated into the plastic both inside and out will permeate it. Dew fall and rain will soon wash the bleach away and all that will remain is the scent of chocolate which is inside the plastic.
This is because ferrerro use food grade plastic of the permeable variety for the kinder eggs and due to the length of storage (at one of my company's depots) it will further penetrate the plastic. A quick wash or even a soaking in bleach wont do the trick you have to totally displace the chocolate from all of the plastic to do this and that will take about the same time as they are exposed to the chocolcate and its smells.
"If you can't be a good example, then you'll just have to serve as a horrible warning."