You will need to get the SQL job to create a fixed name file, we can rename it later.
Machine A runs the SQL backup job, scheduled with a SQL job.
Once the SQL backup has completed Machine A runs a scheduled task that executes FTP_upload.bat to upload the SQL .bak file to FTP service B.
Contents of FTP_upload.bat
Contents of ftptransfer.cfg
Open <ipAddress of FTP service>
Put <full path and name of .bak file> <remote path at location>
Modify the scheduled task times accordingly to fit with the backup and transfer times for your machines / file sizes
Once the transfer has completed, create another scheduled task on Machine A to execute rename_backup.bat
Contents of rename_backup.bat
FOR /F "TOKENS=1,2*" %%A IN ('DATE/T') DO SET DATE=%%B
FOR /F "TOKENS=*" %%A IN ('TIME/T') DO SET TIME=%%A
rename ".\SQL.bak" "SQL_%today%.bak"