The verdict against Maxim Tesli, front man of a band called Shchenki (The Puppies), was imposed by a St Petersburg court on the grounds of "petty hooliganism".
It came less than two weeks after a rapper called Vacio was jailed for wearing nothing but a strategically placed sock at a Moscow celebrity party that caused a national scandal.
In ironic comments on its Telegram channel, the St Petersburg court service described Tesli as "the hero with the sock" and said it was pleased that he had turned up fully clothed to the hearing.
Video published on social media showed Tesli on stage with the sock in place and then briefly naked without it, prompting shrieks from the audience.
"I regret it. It happened by accident. I didn't think that this sock would fall off and it seemed like an appropriate performance, which, of course, was not the case," the court service quoted him as saying.
He separately told an online news outlet, Mash, that his action was "absolutely chaotic" and stupid.
Tesli's punishment came after rapper Vacio, whose real name is Nikolai Vasilyev, was jailed for 15 days last month and fined 200,000 roubles ($2,182) for propaganda of "non-traditional sexual relations" after using a sock to hide his modesty at an "Almost Naked" party at a Moscow nightclub.
The event provoked a powerful backlash at a time when Russia is waging war in Ukraine and authorities are promoting an increasingly conservative social agenda. Many of the stars who attended have since issued public apologies.
Russian media have reported that the rapper's initial 15-day sentence was later extended by another 10 days, and that he has been issued with a summons to appear at a military conscription office.
(Reporting by Mark TrevelyanEditing by Gareth Jones)
By Mark Trevelyan
