If you are using the web version of Google Docs/Slides/Sheets on an iPad and you can't find the toolbar/menubar at the top, it is likely because the document was put in Full-Screen mode.

To exit Full-Screen mode, try pressing the command ( cmd ) key and the period ( . ) key at the same time.

If that doesn't bring back the toolbar,

try pressing the control key and the left bracket ( [ ) key at the same time.

Third option - Try Control, Shift, F