Mark Cuban says this promising Shark Tank pitch turned out to be his worst investment

Billionaire entrepreneur Mark Cuban was on 'Shark Tank' for over 10 years.

Billionaire entrepreneur Mark Cuban has revealed the worst investment he made on business reality TV show Shark Tank.

Mark Cuban spent over 10 years as one of the "sharks" on the show, assessing pitches made by aspiring entrepreneurs. He invested $20 million in 85 startups, according to CNBC, and sustained losses across those deals. But there is one investment that he particularly regrets.

Back in 2013, an entrepreneur named Charles Michael Yim had brought a smartphone breathalyser to Shark Tank. He claimed that the device could provide an accurate measure of blood alcohol content, and the readings could be sent to smartphones.

When connected to a phone, it would give users the option of calling cabs with just a touch button.

The pitch had impressed all the judges, and they agreed to jointly invest in it.

But four years later, Yim was accused of misleading customers about how  accurate his breath analyser was. His company, Breathometer, was ordered to refund everyone who bought their device, CNBC reported.

During a recent interview on the Full Send podcast, Cuban described investing in Yim's business as his "biggest beating".

Cuban accused Yim of blowing the company's money on trips.

"It was a great product,” Cuban said. “But, the guy, I would look at his Instagram and he would be in Bora Bora ... Two weeks later, he’d been in Vegas partying, and then he’d be on Necker Island with Richard Branson.”

“I would text him, 'what the are you doing? You’re supposed to be working,’” he added.

In his defence, Yim said he was networking for his business. He told CNBC at that Cuban's comments were "completely off base".