"It snapped" can be considered a complete sentence, depending on the context. It is a sentence fragment because it lacks a subject, but it can still function as a complete sentence in certain situations, such as when the subject is implied or when it is part of a larger conversation. For example, if someone were to ask "What happened to the stick?" and another person responded with "It snapped," the meaning is clear and it can be considered a complete sentence in that context.
~~~Harsha~~~