The Google Sheets app is compatible with my Android TV - https://play.google.com/store/apps/details?id=com.google.android.apps.docs.editors.slides&hl=en_GB
From memory I believe I can install apps without a password. I believe even changing Google Play to require authentication for purchases will not enforce this for free applications.
So yes - it is possible to access google data via applications.
If this is not desirable then you either need to use a different Google account or use something like AppLock to restrict access to Google Play and any other applications with permissions you aren't happy sharing with other TV users.