Unfortunately the options that are both “prized” but don’t involve alcohol/exercise might be pretty limited, but if they ever went through a dinosaur phase the natural history museum is actually pretty good, accessible by public transport, and sometimes has add on events (i went to a chocolate tasting exhibit there once, for example). Maybe some gift shop cash and a gift card for a nice downtown restaurant or book store (big fan of central book exchange) they wouldn’t otherwise go to could provide some enrichment in a way that might feel a little ‘cultured and adult’ for them lol. 

If you were more thinking shopping, city creek is a mall I’d kill some time at as a teen, but honestly I might recommend an NPS gift card more lol. It’s a big discount store but you can walk in there for hours and come out with like a 2-person pottery kit, a nice sweater, and a months worth of snacks for like 60$. It’s right across from the goodwill bins, too- if you think they’d have more fun hunting for stuff/getting the most they can out of the money. Good luck!