Download the Batman mod pack (often found on community forums or YouTube tutorials). Open your FS20 APK in an editor.

While FS20 does not natively support complex 3D character mods like superhero suits as easily as PC versions, the community uses tools like and ZArchiver to replace existing vehicle or character assets with custom Batman-inspired content. Farming Simulator 20: How to Get the Batman Experience

Replacing trucks with a Batmobile (like the classic 1989 version or the Tumbler).

FS20 is designed for mobile; high-detail mods like a 3D Batman model may cause lag on devices with less than 4GB of RAM.

Since FS20 doesn't have an official in-game mod hub for mobile like FS22 does for PC/Consoles, you must manually edit the game files.