The president can't un-say what he said. But he could go on TV and say
"I made a mistake the other day. I was trying to make an analogy between new medicines, and the disinfectant people use on their floors and surfaces. I muddled it up and people got the wrong idea of what I meant. There are medicines that show some promise this is true, but you should only take them if prescribed to you by your doctor. Only then. Do not take your family member's medicine, do not take a double dose of medicine, do not take medicine you bought on the internet. Only the medicine prescribed to you, by your doctor, and in the dose prescribed by your doctor. And let me be very clear about this: do not drink bleach, or disinfectant, soap or drain cleaner. Do not deliberately inhale any of those things. Do not inject any of these things. Disinfectant is for floors and surfaces, don't even use it on food preparation surfaces unless you rinse it off afterwards. Bleach, disinfectant, lye and so on are poisonous. Let me say that again, poisonous. They will make you sick, they can cause you permanent injury, and they can even kill you if you let them into your body in any way. Once again I apologize for speaking unclearly a few days ago, and in particular I apologize to anyone who took my words as advice. Get in touch with your local department of health, they'll get back to me, and there will be a check with my name on it for you poor people. I'm very sorry and I'll try never to make a mistake like that again."
*astonished silence from press corps*
NYT reporter: Mr President, did you just apologize AND admit to having been wrong? I'm sorry to state the obvious but ...
President: Haha, got you AGAIN. I was just being sarcastic!