Is there a problem with maris ayin to enter a non-kosher restaurant and order just a drink?
Let's say that in the first case the restaurant in question is a fast-food place and the second case is a "sit-down" place. The differences between these two cases would be:
In a fast-food restaurant, the cups are disposable and are not reused, whereas in a sit-down restaurant the cups are non-disposable and are reused after being washed.
In a fast-food restaurant, you don't have to sit at a table; you could order your drink and promptly walk out afterwards, whereas in a sit-down restaurant you would have to get a table, order through a waiter, etc.
Would any of these points make a difference in the din?
Note: I've asked this question to dinonline also, for real Rabbinic advice, as this site is not intended for genuine psak halacha. When the question is, b'ezras Hashem, answered, I will post a link here.