All official Fortnite-licensed physical products have a silver QR code that you can scan to verify the item is an authentic Fortnite product.
Once you scan the QR code, you will be redirected to a website that'll show a code that matches the code shown above the QR code on the physical product.
Once you've confirmed the codes match, you can click Verify, and the website will show a result that the product is an authentic Fortnite product.
Please note that the QR codes on physical Fortnite products are only used to verify authentic Fortnite products; they are not part of a promotion, and you will not receive any additional content by scanning these QR codes.