Suso was responding to his team-mate Jose Enrique posting a photograph of himself getting his teeth whitened.
"What the f*** is he doing? This guy is gay...he does everything except play football," tweeted Suso.
He accepted the charge that he had brought the game into disrepute.
The 19-year-old Spaniard, who has made 13 first-team appearances for Liverpool this season, was also warned as to his future conduct by the FA.