The most common result is a modded version of Grand Theft Auto: San Andreas (which officially runs on Android). Modders replace character models, vehicle skins, and sound files to mimic GTA 5. You get:
Malicious APKs can steal your login credentials and personal data. Gta 5 Android Apk Obb Data Highly Compressed 670mb
No algorithm exists to achieve a 99.4% compression rate. The most common result is a modded version