According to Gamespot, to enter to win one of the free Switches -- which will come bundled with the hotly anticipated game Mario Kart 8 -- you can buy something at any location between now and May 22, and register the purchase via the McDonald's mobile app. However, you don't actually have to buy anything to be eligible -- you can simply email firstname.lastname@example.org once per day to receive free entries. Obviously, the latter means handing over your address to Mickey D's to spam you with whatever it wants, but that's a small price to pay for a free $300 device that's proven near-impossible to track down.
The promotion coincides with the release of a eight new Super Mario Bros.-themed toys now available in Happy Meals. You can scope out all the official giveaway rules right here.