Heinleinekin's is a (strange) beer (in a strange can) available from the Boot Liquor in SQ6. It's probably not a very popular brand as the narrator points out that "These cans of Heinleinekin's have been sitting here since Lazarus!"
A poster for the same brand can also be found at Orion's Belt, although it may be difficult to spot from the darkness.
Heinleinekin's is a spoof on the Dutch beer brewer Heineken. It is also a reference to the sci-fi author Robert A. Heinlein, whose works include Stranger in a Strange Land, parodied with the slogan here. Lazarus refers to Lazarus Long, the universe's oldest living person and main character in Heinlein's Time Enough for Love.
Just like with Ursula K. LeGuiness Stout, the name of the drink is spelled differently on the poster. Judging by the origin of the reference, "Heinleineken" (Or "Heinleineken's") would probably be the correct version.