The Sonix City line of toy cars and playsets was introduced in the later summer/fall of 2012. The playsets come in 2 variations: full playsets and add-on buildings. The Car Wash is one of the add-on buildings for these tiny new micro-car playsets.
There are four add-on buildings: Wreck n' Roll Service Shop, Pass N' Gas Convenience Store, Big Buns Restaurant, and the Mega Suds Car Wash.
Each add-on building features two buttons and snaps down to your existing full-size playsets (Rescue, Airport, Raceway, Construction). I'm not entirely sure about the tech behind these add-ons, but they appear to use similar magnetic sensors as the cars in the way they interact with the playsets.
With the Mega Suds Car Wash on the Rescue playset, it seemed to barely make a noise. I tried re-seating it and it still didn't really seem to do anything. The buttons were non-responsive and the building overhang sticks out way pass the side of the road making it a little awkward of a fit.
The Car Wash did seem to fit better in the open lot of the Sonix City Airport playset. It make some simple car wash sounds and there didn't seem to be a difference in the effects made by each of the buttons.
I paid $7.99 at Target. The Mega Suds Car Wash set came with a little green truck and the small car wash building. The full playsets at Target are usually $19.99 which make them really feel like a better value.
Seems like a bit much for a small plastic extrusion and a simple little truck with a metal surface on the bottom. While I don't find this to be a good value, it does help bring the rest of the Sonix City investment to life by offering new sounds.