From the Cache Monitor under Administration for a Project Source, it is easy to identify to which project does each cache belong or to filter all the caches for a project identifying one of the caches for that project.
One way would be to modify the display of the caches in the Cache monitor so that all the details for the caches are displayed. This shows information such as the Report name to which the cache belongs, the project name, status, last update, cache size, expiration, type and cache ID. With the option 'Complete Information' the columns for Hit count, creation time, last time hit, file name location and waiting list are also displayed.
To view the details for the caches in the cache monitor, Right Mouse Click (RMC) on the window with the available caches, select the view option and select Details.

This is how the cache details is displayed. It is now easy to distinguish which caches belong to which project and, then by highlighting the reports for a specific project it is possible to RMC and select the options to invalidate or delete the caches.

Another way to separate the reports for one particular project would be to use the Filter by Project option. After highlighting a particular cache, right-clicking and selecting the option, only the caches for the project to which that cache belongs is displayed.