The new stainless steel water bottles are all the rage these days, and while fashionable trends aren’t something I tend to engage in, there are real benefits to them over their plastic predcessors. The most important benefit is that you can boil water right in them, eliminating the need for carrying a separate pot when going light.
I was in Colorado a few months ago and as part of an exercise we needed to boil a liter of water. The guys with the plastic bottles had to figure a way to make a pot out of tin foil, boil the water, then get it into a container. Their success level was marginal, at best. For me, though, it was simple. I usually carry some picture wire with me just in case (it can be used for snare wire or for something like this), so I made a loop around the top of the metal water bottle I had and hung it over a fire. While others were rushing around, I relaxed and fed the fire with small sticks. Simple, right?
When making decisions on your kit, always think about things filling multiple needs. In this case, my water bottle was also my cooking pot and purification system.