Other OBB conversions

Conversion of obb files to rar file format

Everything points to the fact that you simply cannot convert Android .obb (opaque binary blob) files to RAR, or any other similar compressed archive. This is due the fact that .obb files should be encrypted during the exporting process using the JOBB tool. But perhaps you can use the  Android Studio for exploring the content, and this may only work for files that were not further protected by their authors.

Open OBB file    Open RAR file