In my perception only "im Urlaub" is commonly in use. The opposite two variants may very well be legit. But I do not know anybody stating "in Urlaub" and I'd say "auf Urlaub" is just slang. Comply with combined with the video clip beneath to find out how to put https://bihlmayermedia-bilder.com/urlaub/wir-sind-im-urlaub/