They are a green milkshake liquid contained in a generic red cup with white lids and white bendy straws.
Role in episode
Patrick orders a Sucker Shake. Once he consumes it, the shake comes out of his cup and sucks on his face. Patrick sucks the shake and swallows it afterward. He then offers one to SpongeBob, who shrieks in panic in response. The drink then flies into Invisible Stan's stomach, and after he swallows it, the drink screams inside his stomach.