It can't even be used in battle.
And V Translaka is pretty much correct. It basically acts as a randomly chosen single target healing item. It can restore 50 HP like a tonic, 200 HP like a mid-tonic, 500 HP like a full tonic, 10 MP like an ether, etc. Even 999
HP and 99 MP like an Elixir
Except that it can also heal 999 HP. There's no item that goes along with that, but if there was, it would be called a HyperTonic!