On June 6th, McDonald's will accept foreign currency for international menu items in the US as part of a promotion.
OK, that's reasonably clever. And I'll admit I'm intrigued by the stroopwafel McFlurry. Further, since many of us would be loath to eat at a McDonald's while abroad, now you can kinda "cheat" and do it at home, without feeling as guilty*! So if you have some spare euro coinage burning a hole in your change drawer, now's your chance to spend it!
*the usual eating-at-McDonald's guilt still applies.