Stash water bottle from Hydrapak is just such a product.
Made from durable and flexible materials, the Stash is a collapsible water bottle designed to shrink down to a highly packable size when not in use. This makes it super easy to stow in your pack until you're ready to use it, at which time it expands back to its full size in a manner of seconds.
I carry the 1-liter version (it is also available in a 750 ml size) of the Stash with me when I hit the road, and I've found it to an excellent traveling companion. It is lightweight (3.1 oz/88 g when empty), and yet still plenty durable enough to survive plenty of use and abuse in the backcountry. My Stash bottle is capable of holding up to 32 oz of water when full, but can reduce down to just 1/5 its normal size when you're ready to tuck it away.
As if that wasn't enough, the bottle can be used to store both hot and cold beverages. It is rated for use at temperatures as high as 140ºF (60ºC) or it can withstand its contents being frozen too. That versatility makes it a great option for the trail or campsite, allowing you to take it anywhere you want to go, and still stay hydrated along the way.
The 1-liter version comes with a wide-mouth (63 mm) cap that makes it extremely easy to drink from. That cap has also been designed to fit most backcountry water filters too, allowing the Stash to be refilled directly from a stream or lake. That same opening comes in handy when you're pouring water out as well, for instance when you're filling a pot to boil water for dinner.
Made from 100% BPA and PVC free materials, the Stash is perfectly safe to drink from. It also doesn't absorb the flavor of liquids other than water either. On occasion, I like to fill the bottle up with water and add a couple of nuun tablets, but after rinsing the bottle out the taste from those tablets usually disappears. You will have to occasionally wash the bottle out however, which is another time when the wide-mouth opening comes in handy.
I have been carrying this bottle with me on numerous trips over the past year, and have come to truly rely on it. I love that it weighs less than half that of a hardshell bottle, and that it compresses down to such a small size. It also draws a lot of attention from fellow travelers and guides, all of whom comment on what a clever and useful product it is. Most want to add it to their own gear collection once they head home.
If I have a criticism of the Stash it is that it often takes two hands to drink from it properly. Because it is a flexible bottle, it will start to bend out from the weight of the liquid inside as you start to empty it. Other bottles will allow you to drink with one hand, as their hard shells prevent this from happening. For me, it is a small price to pay for the other conveniences it brings however, but it is worth pointing out nonetheless.
Speaking of small prices to pay, the Stash bottle is incredibly affordable too. Priced at just $22.99 for the 1-liter version, and $17.99 for the 750 ml model, this is an inexpensive option for adventure travelers, backpackers, and campers alike. It also makes a great stocking stuffer gift for the holidays too, as just about any outdoor enthusiast would love to receive this bottle. It's even available in five different colors.
Versatile, durable, affordable, and just downright cool. The Hydrapak Stash is one of my favorite pieces of gear that I've used in a long, long time.
Buy it at REI.com, CampSaver, or Backwoods.