Here we don't want to talk about ContentProvider and IPC and Intent:
If you want to share data between two applications, what I know is if two applications should use the same process, then they can share data.
How to make application use the same process please refer to:
android:sharedUserId and android:process.
(It's undocumented, but the shared user id need to be a string with at least one dot separator.)
Private Folder / SharedPreference.
SharedPreference and Private Folder are accessible by application context.
If you can obtain the correct context, then you can get data from another app.
This does not require using the same process.