'Shark Tank': This personal assistant quit her job to solve under-breast sweat and her company did over $1M in sales in a year 

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One hot summer day in 2015, Erin Robertson was getting ready to go on a date. There was just one problem: She could not stop sweating once she got out of the shower, especially under her size 32 E or G breasts, "depending on the day, weather, and whatever mood my 'girls' are in," Robertson tells CNBC Make It.

Solving what is actually a common issue for the well-endowed led to Robertson invent The Ta-Ta Towel, and now the company is bringing in seven figures.

On Sunday, Robertson, 35, took her terrycloth halter-style lounge bra (sizes C through H) that wicks away moisture from the breasts and neck to season 10 of ABC's "Shark Tank," seeking $200,000 in exchange for 10 percent stake in her company.

Eric McCandless | Getty Images

Robertson's pitch had clearly entertained the Sharks, who were giggling, and Mark Cuban even proclaimed, "Daymond's going to be so upset he's not here."

But it was the numbers that enticed the Sharks to bite; in 12 months, Robertson said, she sold $1.1 million of the bras.

"You've got to be just crushing it, rolling in the dough right now," Cuban said.

Indeed, it's been a life-changing experience, according to Robertson.

"Right before this happened, I had been a personal assistant for 13 years," Robertson said. "Hated my life. It was a really difficult job. So, I quit, and I was making all of these in my living room.

"I YouTubed 'how to sew,'" Robertson said. "I couldn't even thread the needle or get it in there, and I started making them myself."

Her product went viral online she said, and sales exploded. But she wasn't prepared for the massive increase in interest.

"I did not know what I was doing. Everyone took advantage of that, and jumped on and tried to rip me off and steal, so I had to take a break," Robertson said, adding that she had to enforce the design patent that had been granted to her.

There were other aspects of her pitch that caused concern among the Sharks too, like low margins and sliding sales since The Ta Ta Towel's viral moment in 2017. The sharks also expressed doubt over Robertson's $2 million sales projections for 2018, since the company has only done $188,000 so far. When asked how she was going to make that massive jump, Robertson's lack of strategy prompted some questions.

"Here's the problem, a lot of things aren't adding up right now," Cuban said. "You had this viral moment, that propelled sales in a short period of time to a million dollars. You come into this year, and you don't have the viral moment and you have all the aggravation of shutting down all the knock-offs."

Lori Greiner — known as the queen of QVC-TV for her success in retail products (she's created over 500 products and holds over 120 U.S. and international patents) — saw potential, however.

"You had me at hello," Greiner tells Robertson. "I get it. I get this product."

After Robertson declined Greiner's offer of 50/50 partnership (noting that when she was broke, she had to take on another investor so she in fact, only owned 90 percent of Ta-Ta Towel), ultimately she accepted Greiner's offer of $200,000 for a 40 percent stake in the business.

"After getting the opportunity to be on Shark Tank and get a deal with Lori...I feel like I was just welcomed with open arms into an exclusive club," Robertson tells CNBC Make It. "Lori is the real deal and she is absolutely lovely from the inside out. I'm learning a lot from her and I couldn't be more grateful for all that's happening right now."

Plus, Robertson says the exposure has already boosted the brand: "[S]ales are pouring in," she says. "Never underestimate the power of women; we have brains, brawn, beauty, and boob sweat."

It's not the first offbeat product the Sharks have seen come across the stage. Last season Cuban invested $200,000 in a dating app based on things you both hate and O'Leary invested $150,000 in men's padded underwear.

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This story has been updated to include additional comments from Robertson.

Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank."

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