The unattached midfielder has been with the 20-time league champions for the past two weeks in his bid to keep fit as he continues his search for a new club.
He left Spanish side Deportivo de La Coruna at the end of last season following the expiration of a half-season deal.
“I think Sulley’s decision to train with us is awesome," Noonan told his club's official website.
"It is a credit to the quality of the Hearts brand for the fact that we have kept training in this environment [despite football being at a standstill in this country].
“The reports I have gathered from training concerning Sulley’s positive attitude and professionalism have been amazing.
"Sulley is not only a quintessential professional but a man who has never forgotten where he came from.
“Sulley’s presence will not only inspire our young players to dream big dreams, but it has also shown our players what it means to be a professional.”
On Monday, Muntari reportedly surprised the playing body with a cash gift of $100 per head. Twenty-two players turned up for practice on the day.
On Tuesday, reports say he presented 50 packs of assorted fruits to the team.
Muntari, 33, is in the twilight of a career that has seen him grace the pitch for the likes of Italian clubs AC Milan, Inter Milan, Udinese and Pescara, English clubs Portsmouth and Sunderland and Saudi side Al-Ittihad Jeddah.
The Konongo-born, who represented Ghana at three successive Fifa World Cup tournaments between 2006 and 2014, played for Liberty Professionals during his time on the domestic scene.