Can one make kiddush using a plastic disposable cup? Also, can one use a shnapps cup with shnapps in it that’s less than reviis to make kiddush?
It is better to find a real (silver, glass, china) cup for Kiddush, but where nothing else is available one can use a disposable cup.
For the shnapps question please see here.
A cup used for Kiddush should be made of durable material (Iggros Moshe 3:39), out of respect for the Kol Shel Berachah, so that a disposable cup is not lechatchilah. See also Shut Minchas Yitzchak 18:23, who questions whether a disposable cup can be considered a keli for this purpose.
However, on a bedieved level, where there’s nothing else, one can use the disposable cup.
See also Shut Tzitz Eliezer 12:23.