Obviously (or maybe not?) BPA (Bisphenol A) bottles are only good for peeing in.  You definitely don't want to store drinking water in them especially if they may sit out in the sun. Personally, despite the noise and the weight, my wife and I carry our water in large stainless steel(Klean Kanteen) bottles.  Stainless is inert and won't pollute or affect the taste of water.  For most other stuff I'm fine with hard or soft plastic Nalgene bottles as long as they are BPH free, which most are these days.  I find the hard plastic wide mouth Nalgene's don't really keep oil, ghee or maple syrup from leaking so I tend to use the soft plastic narrow mouth Nalgene's for stuff like that.