Why not use a quart ( freezer) ziploc bag? Cheap, sturdy, already on the 1 q size...
Or better yet, carry a water bottle.

I've read a lot about them. While I haven't tried them yet they have a great reputation. Maybe I'll have to purchase a few and give 'em a shot.

I've been using the Aqua-Pouch's for about 2 1/2 yrs.now,Since I found the Oven(Turkey bags) leak.I consider them to be Essential to All of my Kits,They stand on their own with a Litre of water in em' so Filling/filtering can be readily done,& they have grommet holes to tie some paracord thru them.I have not folded them down to fit into an Altoids can,though I understand they are capable,& retain their resiliency as far as the zip-lok is concerned,should you want to.The large opening accomadates snow for melting,should that be needed,& they are re-usable many time's over,They are Fairly Darn Tough as,far as Plastic goes,& Priced Right,You simply can't go wrong,with these! I have No Affiliation other than, Very Well Pleased with this Invention!

You sold me on 'em, Rich! I just ordered 2 x 3 pack one quart Aqua-Pouches and 3 x 1 liter (the kind with the zipper lock and carry grommets), as well as one prefilter support. I didn't go for the full kit with the purification tablets, but I may add some of my own later. The ziplock 1 liter bags might be more useful overall, given the grommets and the fact that they're more than twice as thick, but you can't beat the compactness of the 1 quart ones that don't zip. Those should fit an altoids tin with ease.

I'm sorry to drag this slightly off topic, but if you try this, you will be one happy camper. Regarding the sock part of this post, I have discovered Merino wool/silk hiking socks made by the Wigwam company. I get mine from REI co-op. They are cool in the summer, warm in the winter, and completely awesomely soft and comfortable on your feet always. Truly cosmic sock experience. They cost about $20 per pair, but in actuality they are priceless IMHO, and wear like velvet iron. Oh, presumably they would soak up a great deal of dew or whatever and squeeze nicely into one of those Aqua pouches, too.

Thank you.