How do I run a sudo command at login/logout on macOS

Unless the files are created with sudo the user can delete files within his own profile.

So, creating a LaunchAgent that cleans the desktop at login would do the trick.

Login in with the account you want to use for guests.

Create a small script with the following code and save it as /usr/local/bin/cleanDesktop.sh.

#!/bin/bash
rm -rf /Users/$(whoami)/Desktop/* 

Make it executable by running chmod +x /usr/local/bin/cleanDesktop.sh.

Now create a LaunchAgent to run your script. Save the code below as ~/Library/LaunchAgent/com.local.cleanDesktop.plist

and run launchctl load ~/Library/LaunchAgent/com.local.cleanDesktop.plist from the command line.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>Label</key>
    <string>com.local.cleanDesktop</string>
    <key>ProgramArguments</key>
    <array>
        <string>/usr/local/bin/cleanDesktop.sh</string>
    </array>
    <key>RunAtLoad</key>
    <true/>
</dict>
</plist>

Warning this code deletes stuff and I did not test it. So use with caution. Also, the user could delete this code. Alternatively you could save the file in /Library/LaunchAgents. Then it won't be editable for standard users. But it will run for all users.