I saw this Russian movie about 10 years ago so it must have been published between 1990 and 2008.
(I think) the movie starts with a nerd/computer boy (12-15 years-old) on a scooter who gets into a shop that sells strange objects. The seller gives him a strange CD/DVD. He meets up with a his friends (they are a group of 4~5) and they decide to watch the disc in a kind of forest near a body of water. They get sucked into the computer and transported through a very weird path with some kind of clouds to an island. They all get separated.
We later understand that the disc seller is actually the one how sent them there: he kidnapps whole lot of children and brain washes them with a red potion (I don’t remember why ). All the brain washed kids are dressed in black shiny outfits and work for the bad guy. The nerd kid and a girl from the group get brain washed (but I think the girl is pretending because I remember that she is given the order to brainwash someone but refuses ) .
The group of friends will try to free themselves and all the other kids. At some point in their journey they meet an old style deep sea diver (Yellow suit I think) who lives on the island and who will help them. He has the antidote (which might be water) to “unbrainwash” people.
At the end they destroy the CD which frees all the children from being brain washed and makes the bad guy goes up in smoke.
I know it sounds a bit weird, I’m not even 100% sure it’s a Russian movie. Finding this movie would be a miracle.