They can fight it out with
Researchers have succeeded in growing brain cells in a lab and hooking them up to electronic connectors proving they can learn to play the seminal console game Pong. Led by Brett Kagan, chief scientific officer at Cortical Labs, the researchers showed that by integrating neurons into digital systems they could harness "the …
Because this sort of stuff is how you figure out exactly how biological neurons really work, at a biochemical level. That, in turn, is how you, eventually, many years and a whole lot of research later, figure out how to fix brain disease, fix traumatic nerve injuries, make brain-machine interfaces, and so on and so forth.
Apparently he's already started work on this, and the initial results on its ability to perform simple tasks are so encouraging that the drunken dish-brain is now odds on favourite to be the next Tory prime minister.
The etymological, technical meaning of "sentient" is "experiencing sensation". Inasmuch as this puddle of neurons apparently responds to changes in its environment, the term is fine.
It's primarily the less rigorous sort of SF which has used "sentient" as a synonym for "sapient", a rather different attribute.
99% of discussions of sentience are irrelevant and misguided. It's not the interesting question.