Here is the format for citing a tweet in MLA 9

Screen Name Last Name, First Name [@handle]. "The entire tweet word-for-word." Twitter, Date Month Year of Tweet, Time of Tweet, URL.

Example:

Fogarty, Mignon [@Grammar Girl]. "Moving that old cup of tea off my desk before I accidentally drink it." Twitter, 11 Aug.  2022, 12:09 p.m., twitter.com/GrammarGirl/status/1557761187097350145.