its for the rear washer fluid...I don't have a sunroof (thank god), so I know its not a drain for that. take off your plastic door sills and you'll see the same hose (driver's side)...it runs the fluid to the top of the rear glass so that you can wash your rear hatch...once you check the lines you'll see
CelicaHobby.com is an independent Toyota Celica enthusiast website. CelicaHobby.com is not sponsored by or affiliated with Toyota Motor Sales, USA, Inc. in any way. The Toyota and Celica names and logos are trademarks owned by Toyota Motor Sales, USA, Inc.