The USA Network may have mistak- misguid- stupidly canceled 'The 4400', but its mythos lives on in Toobworld!
From the '4400 Wiki':
"Promicin is a neurotransmitter - a chemical produced in the brain that relays, amplifies and modulates signals between neurons and other cells. It is set apart from the normal four that control and regulate the human body, providing access to an unknown area of the cerebellum and giving the person access to extra-human abilities."
The Brewmeisters of Bud Light (in the TV Universe only, hopefully!) may have been experimenting with Promicin, manipulating its basic compound so that it can trigger one specific extra-human ability - the ability to breathe fire.
The Bud Light Ad
This specific recipe for Promicin would have been added to the mix for the televersion of Bud Light so that no matter who you were, the ability to breathe fire would be triggered in your genetic makeup. (It's probably buried in our DNA along with so much other genetic junk which the Doctor warned about in the episode "The Lazarus Experiment"; probably an ability we might have developed while we still shared the same evolutionary path as the dragons.)
If this is so, it looks as though it was unfortunately marketed before full product testing could be completed. But as we have seen in the commercial itself, the beer company pulled that specific mixture off the shelves and it is no longer available for general consumption.
So this is a blipvert with a specific place in the Toobworld timeline; what we saw was a historical replay of events which probably occurred over the last twelve months - the new beer was announced; the adverse effects began to appear; and it was taken off the market to avoid further bad publicity.
This type of splainin might also work for the other Bud Light blipvert in the series - in which the beer takes credit for the ability to fly. But I think there's more to the story than that, which I'll get to in another post.
Oh, and just to be as crystal clear as gravy - we are talking about a fictionalized version of Bud Light, not the actual suds you can pick up at the store.