How to clear the app cache on the OnePlus 3T
Turn on your OnePlus 3T
Go to Settings > App Manager
Select the app you want to clear the cache for
After you’ve selected the app, look for the app info screen
Select on Clear Cache
To clear the app cache for all apps, go to Settings > Storage
Select Cached Data to clear all app caches simultaneously
How to clear the system cache on the OnePlus 3T:
Turn off your smartphone
Press and hold the Volume Up, Power and Home buttons at the same time until the Android logo shows up and the phone vibrates
Then let go of the Power button and continue to hold the other buttons
Use the volume buttons to scroll down to highlight Wipe Cache Partition
Press the Power button
Scroll down to Yes and press the Power button
Scroll to Reboot System Now and press Power
Your smartphone will reboot with a cleared system cache