Sinner twice tested positive for the banned steroid clostebol in March.
However, the International Tennis Integrity Agency (ITIA) accepted his argument that the steroid entered his system due to contamination from his physiotherapist and opted not to suspend him.
The World Anti-Doping Agency (WADA) subsequently appealed the decision at the Court of Arbitration for Sport, with a verdict pending.
Kyrgios has been scathing about the ITIA decision in the past and didn't hold back in a press conference ahead of his return to the game at the Brisbane International after an 18-month injury lay-off.
"Tennis integrity right now, and everyone knows it, but no one wants to speak about it -- it's awful," said the Australian.
"It's actually awful and it's not okay. I know that people don't like it when I just speak out about things, be honest about things.
"For a kid that grew up playing tennis, I enjoyed the competition, I enjoyed playing.
"I can get emotional, I can throw a racquet, but that's nothing compared to cheating and taking performance-enhancing drugs."'It's disgusting'
Asked whether he was accusing Sinner of cheating, Kyrgios told journalists to look at the facts.
"He did fail two doping tests at separate times, as well," Kyrgios said.
"It wasn't one after the other -- they were a different time frame, so I mean, if you think that that's the way that it got in his system, if that's how you think it's happened, then.
"But, I mean, if he didn't do anything wrong, then why did they take his prize money and points away? Obviously they found something wrong with it."
With former women's world number one Iga Swiatek also having been suspended for a doping violation in 2024, Kyrgios said the sport's image was being tarnished.
"I just think that it's been handled horrifically in our sport," he said.
The ITIA accepted that Swiatek's violation was not intentional and she received only a one-month ban.
"Two world number ones both getting done for doping is disgusting for our sport. It's a horrible look," said Kyrgios, who has been out of the sport since suffering knee and wrist injuries at the 2022 US Open.
Kyrgios has had wrist reconstruction and said while it was a success, he was unsure how the wrist would cope with tournament play.
"I'm just not going to take anything for granted," he said.
"I'm going to go out there and play. It's literally going to be a day-by-day symptomatic injury moving forward.
"If I play a long match, jam it the right way, who knows how it's going to pull up the next day. That's the type of injury it is."
Kyrgios's comeback begins against rising French star Giovanni Mpetshi Perricard.
