Screwed up a hostel reservation in Berlin, have 36 hours to travel from Berlin to Gothenburg. Any fun ways to make this an adventure?

US citizen, doing solo travel in Berlin and then going to Gothenburg to stay with a friend for Midsommar.

Accidentally set my hostel reservation to check out at 11 am the day before I go to Gothenburg, and my friend cannot pick me up until 8 pm the next day.

Does anyone who lives between these areas have any recommendations for a way to make this fun? I could just extend my hostel reservation one more day but that's no fun.

Overnight train? Cities to stop in for a day? Anything helps as I've never been to any of these places before, thank you!