If you want to purge the downloaded patches on WSUS Server to cleanup / delete unneeded content, then you have to use the following tools;
WSUSDebug PurgeUnneededFiles
WSUSUTIL.exe Deleteunneededrevisions
WSUSUTIL.exe Reset
WSUSUTIL.exe Removeinactiveapprovals (optional)
WSUS Debug Tool: This command deletes all files not needed on the WSUS server.
WsusDebugTool.exe /Tool:PurgeUnneededFiles
***(NOTE: You have to decline the updates first.)
WSUSUTIL.exe deleteunneededrevisions: Purges the metadata for unnecessary update revisions from [...]