I'm not sure about this--there's nothing that can really "sober" up a person that I know of, and I'm sure that it's along the lines of "give him coffee," so it sounds slightly suspicious to me. I mean I know that tea can speed up the metabolism, and pu erh is particularly good for that, so that might help it a bit. (I'm willing to be contradicted on this, by the way, so if someone has better information.) Generally the foods people say to eat while you're drinking are greasy ones, and as pu erh is different than that, it seems to fly in the face of what I'm usually told.
I have, however, read in several places that Pu Erh is very good for helping hangovers. It can't replace common sense, not mixing, knowing your limits, and drinking water in between as a preventative; or yogurt and spicy curries afterwards; but if anyone's so inclined as to get a hangover at some point, it might help. Remember to drink responsibly and always have a designated driver; brewing tea while under the influence is also a disaster waiting to happen, so be careful.