Michelob was a brand of beer, a beverage served on Earth in the late 20th century.
In 1986, time traveler James T. Kirk went out to eat with Gillian Taylor. She ordered a large pizza and a Michelob, Kirk opted for the same, although he seemed surprised at the taste of the beverage when he actually tried it. (Star Trek IV: The Voyage Home)
The presence of the beer in the film was a product placement.
Michelob Ultra was a low calorie option offered and advertised in the early 21st century. (PIC: "Watcher")