I have some android applications which usually have no internet access most of the time but there are some times which they can access internet.
If answer is yes:
logcat
keep error logs)?Firebaser here -
As mentioned in the comment to your main post by Công Hải, How does fabric handle being offline? still applies - crashes will be stored locally until there's a chance to upload them.
It will attempt to send those up as soon as two conditions are met - the app is relaunched after crashing and the device is connected to the internet.