A sleep button shows up on my Mac recently, how to get rid of it?
You seem to have enabled the Dictation or Voice Control features.

You can disable it again by opening System Preferences > Keyboard. Select the "Dictation" tab, and ensure it is set to "Off".

Then open System Preferences > Accessibility. Select "Voice Control" (or "VoiceOver" in earlier versions) in the list on the left, and ensure that "Enable VoiceOver" is not selected.