Turn off YouTube recommendations. On https://www.youtube.com/feed/history, click "Pause watch history," clear the existing watch history, click "Pause search history," and clear the existing search history.

Bonus: It's easy to leave them off permanently :-) You can opt out of other Google data collection on https://myaccount.google.com/intro/privacycheckup/

(Note: if one views those URLs with a content blocker enabled, the toggle buttons may not appear. If you don't see those choices, pause the content blocker, reload the page, and you'll see them.)