This has been discussed on the Dinastia, El Mirador etc etc threads where you will find a lot of information. Depending on where abouts in Fanabe you are, probably the nearest place is Martinez at Adeje (near Mercadona)

Their special offers are on the website

http://www.organizacionmartinez.com/

You could always look at Mastercadena:

http://www.fastroson.com/login.php

and because it's sale time, El Corte Ingles usually have some good deals:

http://www.elcorteingles.es/

With all these you don't even need to go to the store, you can order on line and delivery is free