Business booms for former NFL player Chris Gronkowski after 'Shark Tank'

Former NFL player Chris Gronkowski is well-versed in the athletic sphere, and that has paid off in more ways than one. After trading his football jersey for entrepreneurship, Gronkowski founded Ice Shaker, a company that makes stainless steel shakers that keep protein drinks cold for over 30 hours.

“I started Ice Shaker because I wanted the product for myself,” Gronkowski said in an email to CNBC. “I was at the gym, it was over 100 degrees out and by the time I got there my water bottle was warm and sweating. I saw an opportunity to make the ultimate bottle, a bottle that wasn’t just for the gym or for the office, but a bottle that I can use all day long and everywhere I went.”

To get the product’s name out to the masses, Gronkowski appeared on “Shark Tank” asking for $100,000 in exchange for a 10 percent stake. The former NFL fullback even invited the rest of the notable Gronkowski brothers, Rob, Glenn, Dan and Gordie, who all are or have been professional athletes.

“Why is your name not on it?” asked millionaire investor Barbara Corcoran.

Gronkowski said he wanted to build a product that people wanted. “I didn’t want it to be every time Rob posted, it sold, and that was it,” Gronkowski said as he glanced at his brother Rob, a superstar tight end for the New England Patriots, who just recently announced his retirement.

“Couldn’t you call it, like, the ‘Gronk Shaker?'” Lori Greiner added. “Right? I mean, everybody would be like, ‘Yes!'”

“I thought this was poor advice from the sharks,” Gronkowski added in an email to CNBC. “Naming a product after a person could really hurt the business and limit the demographics. I took this advice and made a custom edition bottle instead and was able to capture the market of customers looking for the Gronk name on the bottle.”

Since its “Shark Tank” debut, the Ice Shaker went from $80,000 in sales in 6 months to over $3 million in sales less than a year after the show’s airing. The company now has a variety of products, including six different bottles and more than 80 different SKUs.

Gronkowski added that being an entrepreneur isn’t easy and is certainly not for everyone. “It requires long hours for little pay, but if you have the passion and drive, [then] you will be successful.”

His advice to hopeful “Shark Tank” entrepreneurs: “The biggest lesson that I learned was that you can never be too prepared. Go over your pitch again and again and make sure you have all your facts memorized. If you know your information, you will be able to pitch your company with confidence.”

Find out if Chris Gronkowski makes a deal on “Shark Tank” Friday at 9 p.m. ET on CNBC.