Hello Guys, I know, this is not the recommended way to do this. But, I do not have another choice:

I've got to set up a cron job that will regularly upload a file to an external SFTP Server (no FTP available, and I do only have a username/password for it but no key.)

Still, I need to set up a cron that will regularly connect to that sftp and upload a file.

sftp <<EOF
put filename
exit
EOF

therefore will not work, because sftp asks for the password, before STDIN is evaluated.

What can I do, to pass the Password to sftp?

Again: I am aware of the potential security risk, but I really do not have any choice here, and the server from which the file is uploaded is protected rather well.