For Funtouch OS 9: Go to Settings--More settings--App manager--More--Show system processes--find the certain App--Storage--Clear data/cache; For Funtouch OS 9.2 to OS 10.5: Go to Settings--Applications and Permissions--App manager--More--Show system--find the certain App--Internal storage--Clear data/cache; For Funtouch OS 11 and higher version: Go to Settings--Apps & notifications（Apps）--find the certain App--Clear data/cache; Note: After the cleanup, all the files, settings, accounts, databases and other information contained in this app will be deleted and cannot be retrieved.