Platypus 2 liter soft water bottle. I love carrying one of these in my pack as a back up for a long hiking run. They collapse as you use water so space is not wasted. I like to have a simple rigged one liter bottle on the side of my pack and have this 2 liter in my pack on top of my gear. When I run out of water in the 1 liter bottle I pull out the Platpus and fill up my 1 liter bottle again.
Platypus Platy Bottle 2-Litre(70 ounces)