APK MOD INFO
Name of Game: Overkill
VERSION: 2.1.0

Name of the cheat, mod, or hack (credits: wendgames):
-UNLIMITED MEDALS
-UNLIMITED BULLETS

Overkill MOD APK 2.1.0 (Unlimited Medals/Bullets)

Download the CACHE file/OBB file. They should be .zip or .rar files.
Extract the file to your sdcard.
Move the extracted folder to the location: /sdcard/Android/obb