The only utterance he made was to ask for a drink of water.

Yes, every sentence can be an utterance but not every utterance can be a sentence. This is because an utterance can be just an action of saying or expressing something aloud which may not be a sentence. However, every sentence (that is spoken) can be an utterance because sentences can be said to be a more 'complete' version of an utterance.

First Utterance was created in 1971.

utterance or diffutterance what is a utterance

utterance = bee-TOO-ee (ביטוי)