Easily doable at various airports. It may require going through immigration but that should be easy enough for holders of most passports. I remember being asked by the immigration officer when leaving the non-Schengen secure area at HEL how long I was going to stay in the EU - to his amusement (and Finns are not easily amused) I said probably about 10 minutes because I needed to buy something from the Moomin shop for my daughter. I'm sure this sort of thing must happen dozens of times every day, if not more. Not necessarily just for Moomin reasons of course.