Sprays are one of the elements in Fortnite that is practically useless.
Sprays are definitely an interesting concept of a cosmetic item, but at the moment there are not many uses, and they are certainly not very interesting. There is information on the web that sprays can gain a completely new function.
In the end, it turned out that this is not a leak, but just a concept of one of the players. Still, it deserves a mention.
Using sprays on other players
A Twitter user with the nickname “nxtpyne” dealing with, among other concepts, a proposal for a new backpack. This one, once worn, would allow other players to spray it.
A really interesting proposition, and could eventually make sprays anyway useful. Of course, the backpack would have to enter the game as part of some challenges, possibly completely free. Rather, no one would specifically buy it, although who knows … It would definitely be an interesting option to pass the time before the game starts.
These types of additives are usually introduced only in the following seasons, as they require much more work than normal cosmetic items. Epic used player concepts a lot, and this one became extremely popular. So it is possible that we will see something like this in the game next season.