I am not a lawyer, so all of this is a layman opinion. If the design on the cups is something done by the set designers or artists employed by the movie, then they own the copyright on that design, as part of the copyright on their movie. You can't use it. An example of this might be the designs on the swords and weapons in the movies based on The Lord of the Rings.
If it appears elsewhere, if you can find it sold by somebody or a picture of it before the movie project was begun, they cannot claim copyright on that element.
If there is dialogue in the movie about the design, they own the copyright on that; you cannot steal their words.
Whether you have violated copyright "enough" is a question for the courts, there are no hard and fast rules and the question is if your intent was to profit off of their intellectual property, and it is often a human judgment (by a judge or a jury) as to whether you intentionally appropriated their intellectual property. I think your question and conversation here prove that you did.
If you insist upon the design that you saw, you should consult a lawyer. The easier route, perhaps, is to use your imagination and come up with your own original design, for which YOU will own the copyright.
I do not recommend appropriating the work of others, ever. Imagination is the job of the author. When in doubt, create your own.