The £100million star was part of Pep Guardiola's squad that won the Premier League title on the final day of the season, leading to jubilant scenes at the Etihad Stadium.
Grealish certainly wasn't alone as he danced on the pitch following the game, and those celebrations have continued through the week.
The England star was in fine form during the club's open top bus celebration and was was seen drinking beers and what appeared to be vodka cokes.
Every time he was handed the microphone he would leave the crowd in stitches - which included when he promised to buy jägerbombs for whoever met him at Manchester restaurant, Albatross & Arnold.
That celebration continued into the night, before Grealish popped up on social media again after jetting to Ibiza to party with Wayne Lineker, Gary Lineker's brother, at the popular resort Ocean Beach.
While enforcing that there's nothing wrong with letting his hair down, Cundy believes that Grealish has perhaps 'left himself open to criticism' - especially as his season is not yet over with England Nations League games coming up.
Speaking on The Sports Bar, Cundy said: "He is allowed to enjoy himself because the ultimate goal this season was to win as many trophies as they can and it's his first trophy right? The Premier League, so I understand it.
"There is a part of me, though, that just worries a little bit for him. There is.
"Enjoy yourself… but I just think that he's left himself open.
"If things don't go well for England over the next couple of weeks, maybe Gareth Southgate looks at it as well, we've got a World Cup coming up.
"There's celebrating and then there's celebrating.
"There's just a part of me that's a bit worried and thinks 'come on Jack, don't do something stupid or get yourself on the front pages'.
"There have been moments before he even joined Manchester City where he has got himself into trouble, during lockdown if you remember."
However, co-host and former Tottenham midfielder Jamie O'Hara defended the Three Lions star, particularly after talkSPORT pundit Simon Jordan branded him a 'moron' for some of his antics post-title win.
"Oh come on," he said.
"He's won the Premier League! All he's doing is having a good time with his pals, who he's become really good friends with at Man City.
"They're having a laugh and a bit of banter, and then he's gone to Ibiza - he knows everyone there and they like him.
"Come on!
"Yes [he has had previous], but Man City knew that when they signed him. They knew what they were signing."