Since the script is started by root, you should not need the password.

Sybase database can be started as the sybase user account using the following:

su - sybase -c "${SYBASE}/install/startserver -f ${SYBASE}/install/RUN_SBSA & nohup"

Hopefully that will help you with what you are trying to start.
(the portion posted came from a script written in sh on Solaris 2.6)