Any website offering a standalone “GTA 5 APK” is lying.

While streaming services like Xbox Cloud Gaming or GeForce Now allow you to stream GTA 5 to your phone, downloading a standalone APK and OBB that runs the game natively is currently impossible. The "APKs" found online are usually one of two things:

While modern PC and console versions of Grand Theft Auto V are large, typically requiring between depending on updates and DLC, a "378 GB" mobile version is technically impossible for current mobile hardware to manage. GTA 5 on mobile - is it real? - Facebook

Rockstar Games has not officially released Grand Theft Auto V for Android mobile devices

: APK and OBB files from third-party sites often contain malware, viruses, or phishing software designed to steal personal data from your phone. Legitimate Ways to Play

: Many files marketed as GTA V mobile are "bottled" with viruses, malware, or spyware designed to steal personal data or display intrusive advertisements.