<SARCASM> I think I may have figured out a tweet's real meaning. Sort of: It's that The Donald is a poor language student and can't even name the letters in his new language accurately, at least not when tired.
"covfefe" = "КОВВ"
which is my best guess for an American (that is, who really knows no other language) learning Russian so he can speak to his new masters, and slightly fumbling the letter names (it's actually fairly close, phonetically). That's a nonsense jumble, but might be an acronym for something in the Foreign Ministry… or ФСБ… </SARCASM>