Answer: Trump having a foul odor is the Emperor's new clothes fact about him. Everyone in his circle knows he smells really bad, but no one dares to bring it up publicly.
Former Apprentice staffer Noel Casler did a damning interview in 2018 during which he disclosed a number of embarrassing facts about Donald Trump including the fact that he wears adult diapers and constantly craps himself.
As per Casler, Trump wears a hard plastic back brace which is why he stands and turns so oddly. He also wears adult diapers and is incontinent.
His incontinence is caused by a combination of his advanced age, and years of snorting Adderall (a low dose amphetamine) and his cocaine use. Incontinence is a known side effect of long term cocaine use, and his notoriously terrible diet of diet coke and fast food doesn't help the situation.
Cocaine reportedly flows freely in Trump circles, including in the White House during his first term. This wouldn't be out of character for a man that grew up in the center of Yuppie culture in New York in the 80s.
His use of powerful stimulants would not only explain why he doesn't need a lot of sleep, but also his high energy level for a man of his age, and his notoriously erratic personality.
On a side note former Trump fixer Michael Cohen also stated that his notorious 'accordion hands gesture' is his tell. When he does that during an interview it means that he's lying or making something up. Keep that in mind the next time you see him talk.
Long time trump bodyguard Keith Schiller was apparently given the nickname 'wetwipes' on set because it was his job to go to the bathroom with Trump to clean him up because he can't bend over properly due to the back brace.
That is if anything Casler said is to be believed.
Trump keeps his staff on a tight leash with strict NDAs to prevent them from talking about his secrets and personal life. He's notorious for suing people into oblivion for talking bad about him and he is notoriously vindictive. So what's strange is that he didn't take an legal action against Casler.
Casler is apparently is the only person on staff at the Apprentice that managed to fly under the radar and not sign an NDA. The fact that he has done multiple interviews about this and that the story was buried instead of him getting sued is pretty damning, as it means that he was probably telling the truth. If he was lying, Trump would have sued him, but if he was telling the truth Trump would have to face witnesses about it under oath in court.
EDIT: Having just re-watched an interview with him, Cassler did sign an NDA but doesn't care and openly violates it. He stated it ended his TV career to talk about Trump this way because no one will hire him now. He's publicly dared Donald to sue him for libel on Truth Social and on TV and he hasn't. Given how vindictive and litigious Trump is that's all you need to know.
Some evidence to support Casler's claims have come to light.
During the Battle of the Billionaires on WWE you can clearly see the outline of a diaper in his pants.
Trump was letting off farts and smelling so bad during his court case with E Jean Carol that it was reported by the news.
There's also a number of youtube clips of his speeches where you can here him farting loudly and those around him make faces due to the horrible smell.
EDIT: Here's a clip of Cassler talking about Trump's drug use. Start here, watch 3 minutes
EDIT: Cassler stated in interviews that staffers would refer to the Apprentice as 'the Shit Show'. Boom mike operators would have to sit there and listen to Trump ripping farts on the monitors.