For Offenburg: There is a bar/Döner restaurant just across the stairs from the main passage underground, where you can grab a beer or another drink. Otherwise not much to see. But you only have 36 minutes, not 45 in Offenburg! The train station has a small bakery, where you also could get a coffee.
For Basel: Since Basel SBB is quite central, you find plenty of restaurants in the vincinity. You might even be able to do a bit boating on the Rhine, if you like that.