In most cases, uninstalling and reinstalling the app will remove the app cache data. However sometimes, when you reinstall an app it doesn’t remove the old app. Therefore you need to follow below steps (device dependent):
Step 0) Uninstall their app, then go through the following steps to make sure data is removed.
Step 1) Navigate to the User's folder (which contains Documents and other folders).
Step 2) Press 'cmd, shift, full stop': this toggles hidden files, so they should be able to see the 'Library' folder (if not, they might have just hidden it).
Step 3) Navigate to Library>Application Support, which should contain a folder called 'Doodle[the app you're supporting them with]'. Delete that folder.
Step 4) Reinstall the application.
Step 0) Uninstall the app by following below steps
Step 1) Click start
Step 2) Click the gear icon, to open Settings.
Step 3) In the Settings window, click Apps.
Step 4) To find the app you want to delete, type the name of the app in the search box.
Step 5) Click on the app name to open the related options.
Step 6) Select Uninstall to remove the program.
Step 7) Click Uninstall again to confirm your intentions to remove the program.
Step 8) Follow the directions in the Uninstall wizard provided by each app.
Step 9) Type %appdata% in the search box on the Taskbar.
Step 10) Select %appdata% in the search options, to navigate to the folder.
Step 11) In the File Explorer window, find and open the folder for the uninstalled app..
Step 12) Select Delete in the toolbar, to remove all the app data related to Doodle
Step 13) Reinstall the app
Step 0) Uninstall the app
Step 1) Open the Settings of your phone.
Step 2) Tap the Storage heading to open its settings page. ...
Step 3) Tap the Other Apps heading to see a list of your installed apps.
Step 4) Find the application you want to clear the cache of and tap its listing.
Step 5) Tap the Clear cache button.
Step 6) Reinstall the app
Step 0) Tap Settings > General > Storage & iPhone Storage.
Step 1) Find the app and tap.
Step 2) Then press ‘Delete app’
Step 3) Go to the App Store to re-download it.