Liam Stacey, 21, of Pontypridd, South Wales, sobbed as he was taken away following the failed sentence appeal hearing at Swansea Crown Court.
Mr Justice Wyn Williams told him he rejected an argument that Stacey had already been punished enough.
He said the Swansea University biology student had admitted an offence, racially aggravated public disorder, of intent.
"He was intending to say what he said and was intending to produce the effect that he did."
Stacey admitted making the comments after the former England U21 international suffered a cardiac arrest during the abandoned FA Cup match at Tottenham on March 17.
It was initially feared Muamba, 23, had died but his heart was restarted following 78 minutes of resuscitation attempts. The ex-Arsenal and Birmingham player has since improved, but he remains in intensive care in hospital.
Police across Britain received complaints following the comments.
Stacey initially claimed his account had been hacked, attempting to delete it, before admitting to police that he was responsible for the Tweets after drinking heavily on the day of the incident.
He reportedly told magistrates he had no idea why he had made the comments and had friends from different ethnic backgrounds.