You will need to get the SQL job to create a fixed name file, we can rename it later.
Step 1
Machine A runs the SQL backup job, scheduled with a SQL job.
Step 2
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
ftp -s:ftptransfer.cfg
Contents of ftptransfer.cfg
Open <ipAddress of FTP service>
<username>
<password>
Binary
Put <full path and name of .bak file> <remote path at location>
quit
Modify the scheduled task times accordingly to fit with the backup and transfer times for your machines / file sizes
Step 3
Once the transfer has completed, create another scheduled task on Machine A to execute rename_backup.bat
Contents of rename_backup.bat
@echo off
FOR /F "TOKENS=1,2*" %%A IN ('DATE/T') DO SET DATE=%%B
SET DATE=%DATE:/=%
FOR /F "TOKENS=*" %%A IN ('TIME/T') DO SET TIME=%%A
SET TIME=%TIME::=%
set TODAY=%date%
echo %TODAY%"
rename ".\SQL.bak" "SQL_%today%.bak"
@echo on