Collapsable Growler

From the link: “Because it’s flexible, you can roll up the bottom until the beer is right at the mouth of the opening, and then put on the cap, which locks out oxygen,”

I'll note that wine-in-a-box already has this nailed. A flexible bladder inside of a cardboard box. Be careful and use the liner only, or put the liner inside of a stuff sack for some more protection. Just save the wine bladders and refill them with beer?

I've transported champagne to a wedding of top of Half Dome in 2-liter pop bottles (pressure-rated, holds carbonation, very light per volume). 6 pounds of champagne and 6 pounds of glass (that would have to be carried round trip) became 6 pounds of champagne (one-way) and a few ounces of plastic RT.

Several tricks: really chill the beer/champagne before transferring. Also, pour very gently. You lose very little carbonation that way. Once capped, you can freeze the beer/champagne and it keeps the carbonation while frozen and later thawed. Then you have a cold drink without any extra ice, just track the melting rate and keep it more or less insulated as you approach serving time.

This makes me wish I was a brainiac like the characters from the big bang theory ….. Taking the temp of the atmosphere dividing it by the amount time until drinking the beer times pi plus the square root of the evaporation of said beer. And you end with a perfectly cold glass of your favorite brew .