The Fortnite Soccer skins were added to celebrate the World Cup for 2018! Each of the Soccer skins can be styled with 1 of 24 possible countries. You just need to purchase one of the skins and you get access to 24 different styles. You can also customize the number that appears on the jersey!
These skins will return from time to time, but there's usually a pretty big gap between when they show up. If you want to grab one of these, make sure to do it when they return. These skins kind of have a "try hard" reputation to them. Meaning that players who tend to use these skins are usually pretty good at the game and build enormous structures the second they are in a fight.
Soccer Skins List
Other Soccer Cosmetics
There were some other soccer themed items that came out alongside the skins.