When logged in to the YouTube app, you can now turn on Incognito. Incognito lets you browse in a session that your account search and watch history won't influence or reflect.
How to browse incognito
As you browse, a persistent reminder will show as a black bar at the bottom of the screen to remind you that you're incognito.
What happens while browsing incognito
While incognito, the YouTube app behaves as if you aren't signed in to your account. Your account activity, like your subscriptions or watch history, won't influence your YouTube experience.
When you turn off Incognito, your search and watch history is cleared. You'll return to the last account that you used before turning on Incognito. Also, none of your Incognito session activity will be reflected on your account.
If you're inactive for more than 90 minutes, your Incognito session will end. You'll then be returned to the last account that you used. The next time that you open YouTube, you'll get a message letting you know that you're no longer incognito.
Everything you do while in Incognito mode is private. So, when you try to do something public like commenting or subscribing, you'll be asked to sign in to complete that action.