https://www.gamespot.com/articles/fortnites-week-4-challenge-guide-secret-road-trip-/1100-6460903/

In Season 5 of Fortnite's challenges, developer Epic Games has introduced a secret Road Trip challenge that allows you to get a free Battle Pass tier, if you know where to look. To do this you need to follow a clue to a specific location. However, there are some steps you need to complete before you can do this. The first of these is to successfully finish all of the challenges from a week for the fourth time, at which point a special loading screen will be unlocked that provides the clue you need to find the hidden Battle Pass tier.

The new secret loading screen shows a bunch of Fortnite characters having a jolly old time at the pool party in Lazy Links. If you look past all the fun and frolicking to the back wall, you'll spot an image of a camel and a drinking cup, along with a picture of the Battle Star--that's the clue you need.