I'm going from Hong Kong to Iceland next month. I've read that everything there, including food, are quite expensive. So my wife and I have been researching on how to prepare meal or snack that we can eat during the day instead of going to restaurant.

However, given we will travel by day tours, I don't think fire or microwave will be readily available during the tours. We can only prepare the meal the day before or in the morning and bring with us in the tours.

We've read that peanut butter/honey with bread, dried fruit and nuts are some good options. Overnight oatmeal may be great but I'm not sure we can keep them cool enough throughout the day and if not, whether this will cause food spoilage.

Are there any other recommendations to have more variety? Thank you!