Marshmallets is an Epic Fortnite Harvesting Tool from the Undercover Summer set. Marshmallets was first added to the game in Fortnite Chapter 2 Season 7.
This cosmetic can be unlocked by completing a challenge in the Cosmic Summer Challenges event. Full list of challenges can be found here: All Cosmic Summer Challenges and Rewards.
Undercover Summer Set
Marshmallets is part of the Undercover Summer set! You can find all of the items that belong to it below.