I'd just treat it as any other text file and open and read it with the built in SilkTest file functions. Set the paths for your Netscape and IE cookie folders, and just do regular file I/O operations on them.
If we are talking about persistent cookies (i.e. cookies that are stores on your hard drive) they are nothing more then a text file. They can be encoded, usually they are.
Basically cookie will contain some type of information that the could be read by the application provider to identify a user. So for the security reason, let say password will be stored as a encrypted string, then the app provider will match this string against the database to identify you.
Non persistent cookies are also referred to as session id or a session cookie. This information usually set in the header field of HTTP response/request messages and it's only exists while the browser connected to the server.
This info is not stored on the disc and can be obtained by parsing HTTP header.
If you need information from a non-persistent cookie (in memory only), you can paste the following into the URL field of your browser to see what cookies have been set.
The cookies are separated by semi-colons.