Check this out to understand why I don't let you have water/soda bottles in class (aside from the fact that they pollute our environment).
A "safe" reusable container means that it was intended for repeated use and therefore made of "safe-R" material.
http://www.plasticfreebottles.com/pdf/Understanding-Plastic-Codes.pdf
or
http://www.thedailygreen.com/green-homes/eco-friendly/plastic-bottles-toxins-water-bottles-460410
