Just as there's the Yo app to quickly say hi to someone, there's the Beer?! app, so that you can ask someone for a drink. The app features a simple menu where you can add the names of your friends, and choose one of them to message. Just like the Yo app, the only thing that you can actually message to your companion is a "Beer?!" which is straight and to the point. Rather than worrying about when and where, the app's only feature is to have message recipients reply "Beer?!" so in response, beer is always the answer.
The app is silly and simple, but if the popularity of Yo has been any indication, it should be just as fun to try out with your friends.