This is a very tough question with no clear criteria for determining an answer.
The classic answer, the Turing Test, in my view fails, because humans beings are not the best at making this judgment. Just as we easily watch a movie (which is really a series of still frames) and see movement, it is challenging to see complex, simulated behavior, and not conclude that there is consciousness or something close behind it.
An artist might tell you it is the creative process used to generate content. This begs the question of how to determine a method used to construct art when all you are given is the art.
Another common criteria involves "consciousness": the argument being that only sentient beings are "conscious" of what they do. There are many classic books on this topic (see Susan Blackmore's Consciousness: A Very Short Introduction for a nice, authoritative overview). One that I read recently and found very interesting and persuasive was Galileo's Error by Philip Goff. In the book, he makes the case for Panpsychism. I've heard good things from friends about Michael Graziano's Rethinking Consciousness: A Scientific Theory of Subjective Experience.
If anyone can come up with a clear, largely-accepted, operational way to determine the difference between a sentient intelligence and non-sentient artificial intelligence, it would represent, in my mind, a major breakthrough in both philosophy and computer science.