I did 2 weeks at a banks HQ in their Derivatives and Swaps dept.
I think the point of short Work experiences is to find out is what you want to do, is REALLY what you want to do.
Two weeks of shredding, drinks machines and more shredding was pretty boring. In the second week, I was allowed to do more; less demeaning work, such as set up correlation curves and finalise swaps, but I realised finance was probably not for me.
I was pretty young at the time, so maybe I didn't get enough out of the experience as I ought to, if i went back there now.