1.) State what is true.
2.) Report that a false or dubious claim has been made. (But only if it's newsworthy, meaning important for the public to know it happened. Otherwise use silence.)
3.) Repeat what the truth actually is.
Now for an example... 2/
There's no clear evidence that hydroxychloroquine, an antimalarial drug, protects against Coronavirus. Donald Trump said today he's taking it, but his doctor would not confirm that, and medical experts have said it could have dangerous side effects. 3/