Because these sinks use a standard PubSub component, administration of the sink node is identical to any other PubSub node. XEP-0060 defines standard PubSub usage and management.
<iq type='set' to='pubsub.coffeebean.local' id='subman2'> <pubsub xmlns='http://jabber.org/protocol/pubsub#owner'> <subscriptions node='message_sink'> <subscription jid='bard@shakespeare.lit' subscription='subscribed'/> </subscriptions> </pubsub> </iq>