Are you looking for something in particular? Which programming language? Is there something that isn’t clear from the documentation in particular?
I’m no expert on Sync Gateway, but it seems like, in general, you could just make a normal REST request using whatever REST tools/library you normally use.
You can directly access the REST API from a standalone Java application using a Java REST client library.
You can also leverage the support for offline operations and multi master sync via sync gateway by using one of the inplementations of Couchbase Lite for Java