Jack Daniel's was a brand of Tennessee whiskey.
Jack Daniel's was among the drinks served at Deacon's bar in Los Angeles, California, Earth in 2024. (PIC: "Monsters")
As of 2255 Jack Daniel's could still be ordered in bars on an alternate reality Earth, including the Shipyard Bar near the Riverside Shipyard in Riverside, Iowa.
James T. Kirk tried to order two shots of Jack Daniel's to share with Nyota Uhura when he first met her at the Shipyard Bar. (Star Trek)
Jack Daniel's was mentioned in the special thanks at the end of the Star Trek V: The Final Frontier credits, indicating that it was the brand of Tennessee whiskey used by Leonard McCoy in his family recipe for southern baked beans.
In Star Trek: First Contact, when Zefram Cochrane offers a bottle of "the good stuff", it is in an old Gentleman Jack bottle, though it is likely just a repurposed bottle rather then surviving Gentleman Jack because it has no label and instead just has "Scotch" written on it in large letters.