Google dorks for searching Google Drive.
Spreadsheets:
site:docs.google.com inurl:/spreadsheets/d/ "<KEYWORD>"
Documents:
site:docs.google.com inurl:/document/d/ "<KEYWORD>"
Files:
site:drive.google.com inurl:/file/d/ "<KEYWORD>"
Folders:
site:drive.google.com inurl:/drive/folders/ "<KEYWORD>"
Obviously, replace <KEYWORD> with the search term.
For example, typing site:docs.google.com inurl:/spreadsheets/d/ "passwords" into the Google Search textfield will redirect you to this search page, with all kinds of goodies.