If I understood rightly, you are looking to build a process in Informatica which would access Sybase DB. This activity has to be exposed as an API and can be called by external applications. If this is the right understanding, you may refer to this thread How to create a webservice with IICS that can be consumed ?
If you are trying to integrate with Sybase using IICS, you can make use of ODBC connector to connect with Sybase. First create a DSN on the machine on which the secure agent is installed using the ODBC drivers for Sybase and then use the same DSN in the connection in Infomatica cloud. Informatica Cloud does not have a specific connector for Sybase.