APH Denmark: Sometimes he wears simple t-shirts, sometimes he wears classy outfits. It all depends on the day honestly (and whether or not he is hung over). His usual military coat is pretty stylish, and I think he would wear less formal coats that are similar to it when dressing casually. Underneath it, though, would be a total mystery.
APH Finland: Finny would look really cute in sweater vests. Kind of like the one he wore in the World Series episode of the nordics, only less formal. The vest would be button up, the shirt underneath would have shorter sleeves, and the pants might be looser.
APH Sweden: I dont know why, but I think that Sweden would look really good in plaid shirts. They would have to be a little longer and looser to accommodate his size, but he would look really good. Especially if the sleeves went to his elbows. His pants wouldn’t be too casual though, since overly loose fitting pants make him feel really awkward.
APH Iceland: It is already canon that he wears Lopapeysas quite often (Icelandic sweaters), and I think he would kind of keep to the sweater thing but with a different style. He might like a looser fitting sweater with skinny jeans or something. His sweater would always have a small design or pattern on it; not too small, but not overly flashy either.
APH Norway: He would be kind of on the hipster side, but not totally. He might wear v-neck shirts and sweaters every once in a while too. When he went out anywhere though, he would always be one classy shit. He would be dressed to the nines in a men’s pea coat and fancy scarves. And he would be the kind of guy to always wear black gloves.