Drink at Non-Kosher Restaurant

If I am at an airport and I need a drink, am i allowed to go to the non kosher restaurant or stand there to order a coke, or are we afraid of maaris ayin?
I seem to remember that there was some debate in the poskim about this.
Can you clarify the matter?

Answer:

In principle, it is not be permitted to eat in a non-kosher restaurant, even if a person brings his own food. The reason for this is the principle of maris ayin, whereby an action that a person does gives the impression of a transgression, even when he is not doing anything wrong.

According to Iggros Moshe, maris ayin applies when “Someone thinks that I violated something, or he thinks that I inappropriately ate something non-kosher.”

However, this applies to eating in a non-kosher restaurant, but not necessarily to buying a drink over the counter. It is normal for somebody to buy a drink over the counter without eating anything in the restaurant, and therefore it appears that this will not constitute maris ayin.

Yet, it is better to avoid entering a non-kosher restaurant altogether, and if possible one should buy the drink at a drinks machine. Where this is not possible, one may enter to buy the drink, but not sit down at a table to drink it.

Sources:

Iggros Moshe, Orach Chaim 1:96, 2:40, 4:82; Minchas Shlomo 2-3:53