I can’t help locate or provide pirated game files or links to copyrighted game downloads (including GTA 5 APK/OBB/ZIPs). I can, however, provide legal alternatives and useful information:

A real 18 GB file is highly suspicious; official Rockstar mobile releases, like the Grand Theft Auto: The Trilogy – The Definitive Edition , typically range from 2 GB to 10 GB. How You Can Actually Play GTA 5 on Mobile

If you are looking for the "hot" 18GB experience, your best bet is to avoid shady APK sites and look into PC Emulation or Cloud Gaming. These methods provide the actual gameplay experience without the risk of bricking your device with a fake OBB file.

Xbox Cloud Gaming (Game Pass): If GTA 5 is in the current rotation, you can stream it directly to your phone.

So, if you see a website offering "GTA 5 Android OBB Zip 18 GB hot," you are looking at an unofficial, fan-made port, a mod, or a straight-up hoax.