Servers run out of disk space too sometimes, but the Server versions of Windows don’t have the handy Disk Cleanup utility installed by default. If you want to get it back, you can run this Powershell command:
or you can follow the instructions here if you’re more of a GUI person.
Both of these approaches install the “Desktop Experience”, which includes Disk Cleanup but also some other clutter that you may not want. For the purists out there who just want Disk Cleanup and nothing else, for Windows Server 2012 and earlier you can get the necessary files out of the WinSxS folder (check here for the relevant directories). However, as of Windows Server 2012 R2 this option is no longer available so you’ll have to just accept the added bloat of Desktop Experience.