The shortest and simplest way:
CD "%temp%\OrYourPath\" && RD /q /s .
This preserves the parent folder, which may have ACLs that you want to keep. If any of the contents are in use, you will get errors. If you want to silence and ignore those, add a
2>nul at the end.
If you want to remain in the current directory, or have a UNC path, use PUSHD + RD + POPD instead of CD + RD.