Larry Kudlow said that "plant-based beer" phrase in the middle of a diatribe against liberals'/Biden alleged plan to limit beef consumption and supposedly other animal products.
The "plant-based beer" phrase is not commonly heard otherwise and was mocked (on the left) for the fact that beer is mostly plant-based.
Having said that, according to Wikipedia, there is a concern among some vegetarians whether beer contains any traces of animal products:
Some beer brewers add finings to clarify the beer when racking into a barrel. Finings can include plant-derived products, like Irish moss, or animal-derived products, like isinglass and gelatin.
Most breweries do not reveal if they do or do not use animal products in the processing of their beers;
Kudlow may have been alluding to this in an attempt at hyperboles, but since he did not elaborate on the beer angle in the rest of his diatribe, we don't really know if that's somehow what he was referring to by "plant-based beer". According to some of Kudlow's critics, his intent wasn't to be clear about any of it anyway...
Amid a blizzard of lacerating social media send-ups, the New York Times columnist Paul Krugman offered a sober analysis of what Kudlow was up to.
“So this seems to be the latest rightwing attempt to smear Bidenomics,” he wrote on Saturday. “There is, of course, nothing about eliminating meat in Biden’s plans; so this is like the imaginary mobs that burned our cities to the ground.
“If you read what Kudlow actually said, he’s cagey – doesn’t say that Biden proposed this, only that some people say this is what would happen. But Fox viewers won’t notice, which is the intention. [...]
It’s all false claims about evil liberals, which the base is expected to believe because it’s primed to believe in liberal villainy. They’re not even trying to engage on actual issues.”
A Vox article found it fit to add that while Biden's plan doesn't say anything about farming or meat it actually should because such studies on the impact of meat consumption of climate change are fairly easy to find. In fact, Fox News (and the Daily Mail) imputed to Biden's administration such a plan precisely because they could find such studies, even though they were not mentioned by Biden's plan:
On Monday, Fox News’ John Roberts admitted the error on-air: “a graphic and the script incorrectly implied it [the Michigan study] was part of Biden’s plan for dealing with climate change. That is not the case.” But it was too late: the graphic had already motivated of the more prominent false claims on social media [...]
However nothing was apparently said in that study about ["plant-based" or vegetarian] beer (and [not] using trace animal products in its processing); that was all added by Kudlow for "making fun of [it]" purposes, it seems.
On the other hand, there are some studies on the impact of beer on climate change that aren't too flattering toward beer (regardless what animal trace products it may or may not contain):
Wine and beer has according to the present investigation low NDCI [Nutrient Density to Climate Impact] indexes, contributing with few nutrients to comparatively high GHG emissions, and have primarily a gastronomic role of the meal.
Apparently the right-wing press hasn't discovered these studies yet... or they might worry that beer could be banned altogether...