The Manual clearly loves GSI's Boulder Flask
"This clear case may look fragile, but the Boulder Flask from GSI Outdoors is completely shatter-resistant. The silicone grip keeps it from slipping (especially helpful if your hands are wet or sweaty), and the top remains connected to the body, so you’ll never lose it. This camp flask weighs just four ounces and, depending on which size you choose, can hold six or 10 ounces of your favorite adult beverage." Read full article here.