With iCloud Drive, you can create files in one app on your iPhone and then open or edit them in a different app on your iPad or Mac. For privacy and security reasons, however, you can also control which apps can access your iCloud Drive files.
How to revoke iOS app access to iCloud Drive
Launch the Settings app on your iPhone or iPad.
Tap on iCloud.
Tap on iCloud Drive.
Scroll down the list and turn Off any app you want to prevent accessing iCloud Drive.
Turn Off access to any apps you don't want to use iCloud Drive with.
How to revoke Mac app access to iCloud Drive
Click on the menu in the top left corner of your Mac.
Click on System Preferences.
Click on iCloud.
Click on Options... next to iCloud Drive.
Uncheck the apps you don't want to have access to iCloud Drive.