What is the appropriate thing to do in this situation?

In the first place, you're stressing way too much over ONE day in a cl. If someone invited you to a party at their house, they would provide the food so just look at it like that. I know everyone else is bringing something, but remember in potlucks there is always way too much food. No one is even going to notice. And if you think about it, you are going to eat a meal at school that you would normally have paid for yourself. Why don't you see what that amount of money can buy? It doesn't have to be something that feeds all 35 people in the cl (an example). Or it can be the cheap thing like the napkins. You know,...most teachers know that most students are short of cash. I'm sure others in the cl are in the same or similar position only you don't know it. Perhaps it's also time to simply make the sacrifice of a few extra dollars for this cl activity to avoid the discomfort you will clearly feel, OR accept that most people know students are strapped for cash, enjoy the bratwurst, and be done with it. I would have made a joking/real comment like, "OK, I'm signing up for napkins because I'm totally broke!" Something to let others know where you stand. But the long and short of it is, make the sacrifice if you need to. You really shouldn't take the "living on a shoestring" philosophy so literally when travelling to other countries. You should always have some emergency money/credit card you can access if you need it, or a parent or friend who could send you some extra cash to help you with your travelling experience, and you can pay them back when you return. It's not that big a deal, so try not to make it one in your head, and you'll have a better time at the party and do better in school. Good Luck.