This holiday, you can put your unwanted gifts to good use -- and get some free food at the same time. Burger King is offering customers the chance to exchange unwanted holiday gifts for a Whopper on Dec. 26.

In the U.S., its restaurant located at 910 Arthur Godfrey Road, Miami Beach, Florida will be offering the deal between 10:30am and 5pm on the day after Christmas, and restaurants in London and Brazil will also be running the promotion. Burger King will donate all the unwanted gifts to charity.

If you don't live in one of those places, you can still take part on social media; the first fans to post a picture on Twitter or Instagram with their questionable gifts using the hashtag #WhopperExchange will get a "surprise" from Burger King's social media accounts.

AKQA Brazil is responsible for the campaign.