Collapsible water bottles! Great for booze or just water. The are nice because they clip on your belt buckle and you don't have to carry them. Also cheap so if you lose them it's not like losing a nice Nalgene bottle.
http://www.amazon.com/Reusable-Collapsible-Foldable-Water-Bottles/dp/B00AXD67TW/ref=sr_1_20?s=sporting-goods&ie=UTF8&qid=1427407936&sr=1-20&keywords=collapsible+water+bottle