It is definitely possible to access app sandboxes via an AFC client such as iFunBox or iPhone Explorer.
To emulate the criticized aggressive cleaning of iOS 5.0 you would empty the […]/Library/Caches/ and […]/tmp/ directories of the involved app(s), but due to the manual access involved one can perform a finer-grained selection.
The PhoneClean app also performs fully automatic or app selective cache cleaning.