In Fortnite, a "sweat" is someone who seeks to flaunt their skill in the game even when it's not required, and some skins are characteristic of the class.
The term "sweat" comes from the idea that these players exert so much effort to show off, that they generate a lot of sweat. These players will do whatever it takes to win and normally put more hours into Fortnite than regular players.
Over time, these players started to main skins that were smaller in frame, so as to become a more difficult target to hit. Fortnite skins associated with sweats, particularly those unavailable for use by regular players, are particularly common. Most sweats are identified by the skins shown below, but they make use of plenty of other less common skins as well.
5 Fortnite skins that sweats use the most
#5 - OG Defaults
If spotted in a game of Fortnite, this is a dead giveaway. Normally, when players wearing a default skin build upwards quickly after being shot at, it’s a sweat. Female skins are sweatier than male skins, due to their smaller stature and frame.
The most common is Commando, mostly because many streamers have used the skin and declared it a "sweaty skin."
#4 - Siren
Siren on its own was not a sweaty skin, but that changed after a pro-Fortnite player began to main it. All thanks to Benjyfishy, this skin has become one of the sweatiest skins in all of Fortnite.
This skin became his go-to, and the bundle that followed made this an easy purchase.
#3 - Crystal
Made famous by Bugha, the Fortnite Solo Cup champion back in 2019, he said that this was his primary skin at one point. The skin is a dead giveaway for people who want to look like Bugha and many will simply buy this skin and use a pseudonym similar to "Bugha."
If another world champion can name a different skin their primary, this one would potentially be replaced. Until then, this skin isn’t going anywhere anytime soon.
#2 - Aura
One skin fans usually expect to be sweaty is Aura. Aura has become the primary skin of several pro Fortnite players and sweats across the globe. Players who play with Aura as their main skin are either really good, or merely think they’re really good.
#1 - Soccer skin
Perhaps because Fortnite releases a new soccer skin every so often, this one is the most true to a sweat. There is no definitive answer to why sweats choose this skin over many others, but they just do. Every soccer skin, regardless of its color or type, is widely known to be the ultimate sweat skin.