Mini Kegs.

[Agentgonzo]

You can make them last more than a weekend by not opening the top valve to release the pressure - but if you do, you just get a glass of foam

Case in point.
And this is the best I've got it since I opened the keg last week!

 

[Zoiks]

Bought of one of those fass frich party taps (which since rusted as a 5L party keg from cold town beer exploded and rusted the tap) but the above looks very familiar.