This Was Mark Cuban's Worst 'Shark Tank' Investment (and Richard Branson Fell for It, Too)Cuban said a questionable work ethic and one too many "networking" trips contributed to the company's downfall.

Mark Cubanhas made a number of investments during his decade-long stint on ABC'sShark Tank— some of them better than others.

In aninterview with theFull Sendpodcastlast week, Cuban revealed his biggest investment loss to date: $500,000 on theBreathometer, a smartphone attachment that entrepreneur Charles Michael Yim pitched as "the world's first smartphone breathalyzer" in 2013. Cuban discussed what went wrong — and how billionaire entrepreneurRichard Bransonwas tangentially involved.

Yim声称他的呼吸计可以传输BAC-level readings to a user's phone and provide the option to call a cab if the reading was too high. The entrepreneur gave all of the sharks glasses of champagne to test the product for themselves, and all five of them were in — a first inShark Tankhistory, perCNBC Make It— giving Yim $1 million for a 30% stake in his company.

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ButCubanquickly realized he had a problem. "The guy – Charles – I'd look at his Instagram and he'd be in Bora Bora ...," Cuban toldFull Send. "Two weeks later, he'd been in [Las] Vegas partying, and then he'd be on Necker Island with Richard Branson."

When Cuban pressed Yim about his whereabouts and work ethic, the entrepreneur claimed he was "networking."

"Next thing you know, all of the money's gone," Cuban said.

In 2016, Yim shifted his focus to Mint, which claimed to measure levels of sulfur compounds in the mouth to evaluate bad breath — a product that is also not available today.

But Yim told CNBC Make It that Cuban's accusation was baseless, as he was on Necker Island to pitch the Breathometer toRichard Branson— who did name the product a 2015 finalist in his Extreme Tech Challenge Pitch competition.

Still, it would turn out that the technology wasn't actually sophisticated enough to support Yim's claims. In January of 2017, theFederal Trade Commissionfiled a complaint against Yim and Breathometer, which it alleged, "lacked scientific evidence to back up their advertising claims." Breathometer and the FTCreached a settlementlater that month, requiring the company to notify and completely refund everyone who'd purchased the product.

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Yim admitted he did not conduct proper testing for some of his products, and claims that was the primary factor in the company's lack of progress, per CNBC Make It.

But Yim is still holding out hope: He says the Breathometer has recently been acquired, though details for the deal don't seem to be public.