He is demanding Biden must take a drug test in order to participate in the debate.
He is definitely making excuses in advance, as he does when he thinks he's oing to lose.
He may also be trying to avoid participating, because his actual performance as president and his inability to think will be exposed in a debate format.
Biden will probably ignore it. But he might set conditions of his own. An independent psychological evaluation would be worth doing before every election. Are the candidates of sound mind? Can they pass a test of their brain function? Do they exhibit signs of senility, narcissism or sociopathy?