I’m not obsessed with the “hydration” craze but as a traveler, I have always carried water. Long ago I carried a metal canteen. (You’ll see it on this page.) Then I was stuck carrying 1-liter plastic water bottles. Now, I have the HydraPak Stash. Very light. Folds down. Very convenient. I’m hoping to have the HydraPak Stow soon as well. Also discussed here.