The Russian Sleep Experiment was a fictional story written for a website. If this experiment had actually happened, there would be more documentation to support it than a single article posted in recent years. Also, the ending of the story makes it pretty clear that it is a work of fiction.
The story of the Russian Sleep Experiment as distributed by email around 2010 purports to be the real account of five Russian prisoners who were kept awake for weeks with an experimental gas stimulant and ended up destroying each other in primitive fashion. Snopes, which specializes in researching urban legends, investigated the story and discovered that it is completely fiction, originating in a longer form at a site called the Creepypasta Wiki. The wiki collects fictional horror stories of this sort that purport to be true, with the intent of having them copied onto numerous discussion boards and social media sites.
The Russian Sleep Experiment is one of the goriest, horrifying, cruel and inhumane experiments on record, but I don't believe it actually happened. While it sounds plausible that researchers could subject other humans to such terrible conditions, I don't see how the victims could have mutilated their bodies so severely without having died in the doing.
A relatively persistent tale, oft repeated online, involves a sleep experiment allegedly performed in the Soviet Union in the 1940s. As the story goes, five political prisoners were kept awake, and never allowed to sleep, in a sealed chamber with gruesome results, reminiscent of a slasher movie. No concrete evidence exists regarding the experiment. Reputable investigators who looked into the contentions universally conclude that the so-called Russian Sleep Experiment is an urban legend.