This is my theory.
On top of the roof, near the antenna, there is a slight gap between end of roof and the trunk top. Water is meant to go through there, and escape from under the rear bumper. Somehow it reaches the spare tire area. When i got delivery of my car, every time i washed it, water used to stay inside the doors and leak from the rubber seals. Suzuki sucks big time in quality.
And, i am not sure about the smell, first time happening to me :L.
What i hated about my first complain, they got a water bottle and showed me that it doesn't leak.
I told them straight up, mate, i'm busy. I am not a warranty hwore who's gonna show up everyday just because i got a car in warranty. You gotta fight for your rights hehe