Case- Bill to Bangaldesh and Ship to Maharashtra

Hello Team

We need your expert opening on below transaction

One of our Bangladesh  Customer has raised purchase order for  Robots  to in India A supplier (Uttar Pradesh) and A supplier has raised Invoice to Bill to Bangladesh customer and ship to B Customers(Maharashtra). in this case material will reach at B Customers for trial and testing purpose.

Now B Customer want to sent back to this material to Bangladesh customers then which documents are required for it ???

Please advise ..

Regards Kiran