Message in a commercial: "Our beer goes down easy, like a bankrupt boxer.

Message in a commercial: "Our beer goes down easy, like a bankrupt boxer."

It is making a joke by suggesting the beer and the bankrupt boxer both go down easy, but of course the reader knows that they go down easy in different senses; the equivocation is so obvious that the joke is funny; the boxer goes down easy by being easy to bribe into intentionally losing the fight, which has nothing to do with how the beer goes down easy. 

This analogy attacks the beer as being too easy to drink. A reader wouldn't expect such a silly comment, so the joke is funny by upsetting our expectations.

In this pun, the suggestion is that beer drinking leads to bankruptcy. Since this is so obviously false to the reader, the shock produces a successful joke.

In this parallel between beer manufacturing and boxing match fixing, the suggestion is that both processes are relatively easy. Since it is surprising to the reader that both are easy, this makes for an effective joke.