What Died in my Car?

I was driving in my car after work.  It is hot out there.  I caught a smell of something.  It smelled as if something was rotting.  I ignored it.  Later, I smelled the aroma again.  I looked in the back.  I found what was.  I had brought a banana smoothie to work.  By the time I arrived, I was done.  That was Wednesday.