This article explains how to use Guest Mode on Google Assistant.

You can think of Guest Mode as Chrome's Incognito mode for Google Assistant. It lets your guests use Google Assistant on any Google Home device on your network without their activity being recorded or stored to your Google Account.

Guest mode provides privacy for your guests and prevents preferences and saved settings in your Google services from being adjusted or changed based on requests from your guests.

It's easy to enable or disable guest mode.