This will not show you as active. Teams and Slack and check the presence of HID events. If you have Xcode/swift installed you can script this instead:

    #!/usr/bin/swift
    import Foundation
    import AppKit

    let source = CGEventSource(stateID: CGEventSourceStateID.hidSystemState)
    CGEvent(keyboardEventSource: source, virtualKey:  0x37, keyDown: true)?.post(tap: .cghidEventTap)
    CGEvent(keyboardEventSource: source, virtualKey:  0x37, keyDown: false)?.post(tap: .cghidEventTap)

This simulates one press/depress of the command key (0x37). The rest of the key codes can be found in Events.h in the location of your MacOS SDK library (deep in Xcode usually).

Add it to a cron job or whatever.

I haven't used Caffeine but used the very similar app Amphetamine and found it worked great.

https://apps.apple.com/us/app/amphetamine/id937984704?mt=12

macOS has `caffeinate` built in as well.

https://ss64.com/mac/caffeinate.html