Every time TrumPutin opens his mouth, he says something stupid. Or sarcastic.

The difference is that when he says 
something stupid, nobody corrects him. Good people among the White nationalists; or I knew it was a pandemic before anyone else, even while I was telling everyone it was a hoax and not a pandemic, which was when I was cheerleading for the nation, by telling a lie, which everyone knew was a lie. No one corrects those stupid lies. 

Sarcastic is when one of his sycophants tells him, in a very supportive way, that he has said something stupid. For instance, when he says that  drinking Lysol or Clorox is a cure for the virus, or Noble isn't the way to spell the prizes from Finland or Denmark, or wherever the prize that Obama stole is from. 

So, really, stupid and sarcastic are the same thing, only apparent to his sycophants in different timeframes. 

Sarcastic is an excuse that he can employ when he says something that makes even his sycophants cringe, he can joke that he didn't mean it. That he was being sarcastic. 

As usual, he lies, first because he doesn't know what sarcastic means, and second, because he is most at home with stupidity, not sarcasm. 

He is, though, entirely caustic. And vile. And stupid. And a liar. But not sarcastic.

Make America whatever ...