https://www.gamespot.com/articles/free-fortnite-battle-pass-tier-available-by-comple/1100-6460763/

Season 5 of Fortnite: Battle Royale rolls on with yet another set of challenges to complete. Just as in Season 4, finishing all of the challenges in a given week will complete a corresponding Road Trip challenge. This, in turn, rewards you with a special loading screen that points to a free Battle Star hidden somewhere around the island, giving you an easy way to level your Battle Pass up by one tier.

Three sets of weekly challenges have been released thus far in Season 5, the most recent of which tasks players with following a treasure map in Flush Factory and shooting clay pigeons, among other activities. If you've managed to complete all three sets of weekly challenges to date, you'll earn the third special loading screen, which features a group of characters racing rather unsafely in the new golf cart vehicle. You can take a look at it below (via Fortnite Insider):