I am interested in carrying a glass water bottle on backpacking trips, because I like good tasting, healthy water.

Last time, I took a VOSS glass water bottle, which is really heavy. The plus side, is that I was able to put the bottle leaning on a rock in the fire pit, and heat up some soup (without the plastic lid). It didn't crack, and it was fun to watch the soup circulate in the bottle. The soup on the side closer to the fire moved up the bottle. I guess you could do the same with stainless steel.

Unless someone can convince me that their foldable water bottle doesn't add anything bad to their water (even if they say BPA free, bound to release other yuckies). Is there a plastic capable of not polluting your water?
What I mean by foldable water bottle:
http://www.bellahoo.com/catalog/1500-1999/1674-Foldable-Water-Bottle_1200.jpg

Or that a vintage leather water bottle is the way to go (how are they coated on the inside?). http://www.ampro.co.nz/products/lake/PK1000.jpg

If not that, I would like to know the lightest weight water bottle, that still has a protective sleeve. I just sent an email to Lifefactory to ask how much their 22oz bottle weighs when empty.

I started this thinking glass was the way to go, but I'm open to a good conversation. For example, a stainless steel water bottle doubles as something to cook soup in. Can you then go without taking a pot? Wouldn't a stainless salad bowl be a better multi-purpose pot/pan?

Should I move this topic out of the lightweight zone, since lightweight is a secondary consideration? I do want to find the lightest solution that fits the other considerations.