Who says water bottles need to be made from hard plastic? If you’re packing light and compact, the Platypus SoftBottle is your best bet. They’ll roll up for easy storage when not in use, and still fit just about anywhere when full. These bottles are surprisingly tough, and the flexible construction contributes even more to their durability.
They’re also 100% BPA-free and extremely light-weight (most weigh around a single ounce). Available in various capacities with either a full closure cap or the new dual-valve HyperFlow cap.