Not good!
I have had water ingress a couple of times with A6's in general.
On all the ocations, they were caused by blocked drain holes in the baulkhead.
On my 2004 RS6 last week the tube froze between the bonnet and the engine bay, this caused the hose to pop off.
I thought the squirters were just frozen. It was not until I had run out of screen wash that i checked the pipework. Just as well my baulkhead holes are clear.
What I'm saying here is maybe your screen wash pipe has popped off and your drain holes are blocked leaking into the passenger floorwell. hence the smell of screen wash fluid.
By the way you need to do the following urgently, you need to-
A:- source of the leak (water ingress) .
B:- Get the carpet lifted up to drain out the water and dry out.
If you don't then expect your alarm, central locking etc to pack in, in an a couple of weeks.
I have had to pay for two Comfort modules due to this as they are under the passenger seat. At £275 each, not good!
Yes I agree,What a stupid place to put it

! Audi?
Hope this helps
Coullboy