Use Oracle SQL Developer. I'm presently working through a JDBC connection to a Sybase ASE database using this tool. This seems to be Eclipse-based, but is quite responsive and allows you to view source code for functions and procs too. There is also a debugger available.
To create a new Sybase connection, on the "New / Select Database Connection" window, just click on the Sybase tab, enter your hostname/port/username/password, choose a database to access, and that's it.
And this software is free of charge! One thing I love about Oracle is that they give away so many good stuff for free (think JDeveloper IDE for ADF, JRockit JVM and Mission Control, and this tool).
http://www.oracle.com/technology/products/database/sql_developer/index.html