I cannot identify the math themed collection, but the story you describe certainly sounds like Joe Haldeman's All The Universe in a Mason Jar.
For one thing, it is about an alien who can only consume alcohol.
After a rather grim period of transition, the denizens of Earth
settled down to concentrating on being good, trying to reach Class 3,
the magic level.
It would take surprisingly few generations. Because humankind had a
constant reminder of the heaven on Earth that awaited them, as ship
after ship drifted down from the sky to settle by a still outside a
little farm near New Homestead, Florida: for several races, the
gourmet center of Sirius Sector.
There is some mathematical content in the story, when the retired-math-professor hero is trying to communicate with the alien.
This has been asked before (Looking for a collection of short stories that involved math as underlying theme in every story) but has no accepted answer. (The asker never returned to the site.)
If you are not the person who asked about this before, it means that this anthology almost certainly must exist, and just not be listed in isfdb. That database lists only "Infinite Dreams ", "Flying Saucers", "UFOs: The Greatest Stories", and "Subtropical Speculations". None of these are math-themed.