Some of my Candy Cane ponies smell vaguely sweet but none of my Sundae Best ponies smell like anything in particular. My Cherry Treats smells, of course, of Play-Doh. Most of my Sunshine ponies work though! I think one of them is permanently stuck in a half-changed state but she's pretty like that so I don't really notice.
I have the mankiest Majesty ever that I keep displayed purely because she has perpetual "new pony" smell. I mean, she looks like she was dredged from a river, why does she smell like I just opened her?
EDIT -EVERYTHING should smell of lavender. EVERYTHING. Well, everything that doesn't smell of coffee, anyway.