Google Trends data shows Trump's "Sleepy Joe" name-calling isn't generating nearly the buzz "Crooked Hillary" (or "Little Marco") did in 2016. Base voters who relished doubting President Obama's birth certificate aren't questioning Biden's.The reason that "Sleepy Joe" is a failure is because it is poor rhetoric. It is poor rhetoric because it is not based on the truth and therefore misses the target. Hillary is crooked. Marco is a dwarf, both physically and politically. Joe Biden, for all his various flaws and shortcomings, is not a narcoleptic.
Other factors are working against Trump's playbook. Tech platforms are increasingly moving to shut down hate speech and flag misinformation, killing the sources of some of Trump's favorite conspiratorial material. And search metrics suggest that, for the most part, a nation with more than 125,000 dead from the coronavirus has less patience for the president's usual tactics.
I suspect that the President's original choice for Biden is "Creepy Joe", but he was talked out of using it by his advisors, because they thought it was too harsh. Which, of course, is wormtongue-speak for "too effective". But Biden is a confirmed creeper and women, especially young women and little girls, observably find him creepy.
Even "Sniffy Joe" would have worked, given Biden's predilection for hair-sniffing. But "Creepy Joe" is the killer rhetoric that Trump should have used, and it won't surprise me if he begins using it once his reelection campaign actually begins in earnest.