"Bar Rescue" star Jon Taffer is releasing his own line of hard seltzer to compete with White Claw -- and tells TMZ he spotted a major flaw with WC ...the flavors are weak!!!

Taffer just launched Taffer’s Mixologist Sparkling Craft Cocktails -- clearly hoping to capitalize on the hard seltzer craze that led to a national shortage of White Claw.

FYI, hard seltzer sales have reportedly crossed the $1 BILLION mark over the past year (mostly due to White Claw sales) -- and Taffer saw the perfect opportunity to jump in.

"I've been working on this for a year," Taffer told TMZ in New York ... "perfect time to bring my hard seltzer to the marketplace."

So, how the hell can a new brand compete with such a monster in the space? Taffer says White Claw has a major Achilles heel.

"I think they had a good viral hit. I think they got into the space nice and early. But, I also think there are some weaknesses in that brand, flavor profiles and things like that."

In other words, Taffer thinks White Claw tastes like White Crap.

"So, what I did after 185 Bar Rescues, I came into this with flavors! Things like Cucumber Jalapeno and Strawberry Basil ... so I really came at this with a flavor mentality, not just a money mentality."