I had this problem in my Lexus IS250. It drove me nuts. I cannot stand that smell. For the summer months I ended up buying one of these:
http://www.tooltopia.com/uview-590160.aspx
And a case of these:
http://www.tooltopia.com/uview-590250-12pk.aspx
Basically, you put the bottle of fluid into the machine, turn it on while in the car is on in AC / recirculate. It kills the smell for several weeks. Maybe long for you, but for me, it's was a few weeks. After which I'd run it again. Totally worth it. If my new BMW develops the same smell as my old Lexus I'll be using the same machine.