Barrel is one of the three skins released in the fourth part of the MadJawZ's Shop offer. It could be purchased as part of an item deal in mid March 2020.
Barrel could be purchased for $9.99 in a limited time deal that included 13000 coins and 900 DNA. It was not available for individual purchase and may not be available for purchase in the future.
Details of this skin may vary depending on location, platform or time.