Investigation of an Android backup file:

Create a backup file:
adb backup -f `date +%Y%m%d`_backup.ab -apt -obb -all -system

Extract its contents:
dd if=~/android/20161101_backup.ab bs=1 skip=24 | zlib-flate -uncompress > x.tar

Find resource hogs (as root):
find -exec file '{}' ';' | grep "ISO Media" | awk '{ split($0, a, ":"); print a[1] }'

Android apk files are located in /data/app, they can be (temporarily) removed when there is not sufficient space for installing new apps.