https://blogs.sap.com/2015/05/29/updating-exchange-rates-automatically-in-sap-business-one/

 Using DI API:

 https://blogs.sap.com/2015/05/29/updating-exchange-rates-automatically-in-sap-business-one/

Using B1IF:

https://blogs.sap.com/2015/06/23/how-to-import-exchange-rates-using-b1if/

Using Service Layer and HANAXS:

https://blogs.sap.com/2018/08/27/update-sap-b1-rates-using-hana-xs-and-servicelayer/