Question

How does this sentence demonstrate an unusual use of syntax?

Danced the night away, the excited party-goers.

Answer 1

It's an example of inverted syntax, by putting the subject at the end of the sentence. Yoda is probably the best known example of these sentence structures.

Answer 2

There is no specific predicate or verb in the sentence. There is only an adjective phrase that describes the excited party-goers.

Hope this helps :)