User blog comment:Hybrid Shadow/The 1000th Hunger Games/@comment-5338425-20130212080822/@comment-5824375-20130212082108

The sanity potion can be found in the Cornucopia but there is only 1 and it is in a random pack. Other then that, the only other way to get a sanity potion is by sponsoring but it's going to be super expensive. You see, the sanity potion keeps the tribute from going insane for a while. The Arena's purpose is to drive the tribute insane. Basically, the Games is a test to see how long the tribute can stay sane, that's why the sanity potion is so hard to obtain.