How do I log out of Apple TV on my iPad?

1. Reveal the sidebar in the TV app, if it isn’t showing already. The toggle is in the upper left of the main screen.
2. Look at the current account name in the bottom of the sidebar.
3. Click there to show some account info, including a Sign Out option at the bottom. You may have to scroll a bit.
4. Then sign in again with the wanted account.

iPad is meant as an individual device. You can’t switch Apple ID accounts on there at will. There may be a cool-down period of up to 90 days, depending on the last account change. View and remove your devices that are associated with Apple ID purchases - Apple Support