Well, the bar for sentience is actually so low I am quite sure bacteria and even individual cells in multi-cellular organisms pass it - almost every living cell detects aspects of and reacts to its environment.
It is indeed incredibly low. Slime molds [0] can pass it. There is a memory component, which would prevent single cells from passing it, but it's not a metric that is all that useful in determining the intelligence of a species.
Plastic has memory, but not feeling/sensation nor interaction with the environment. It is also not living by other standards (self-sustaining, reproductive).
