My friend is a student in Germany who is on a student visa. I want to surprise him on his birthday by turning up at his house on the day. When I apply for a visa, should I apply for a Tourist visa (Visiting friends or relatives) or should I apply for a Tourist travel (no visit to any relatives/friends)? I don't want to get any invitation documentations from my friend since it wouldn't be a surprise then. I will be sponsoring the entire trip myself
A Schengen visa is a Schengen visa, there are no strictly defined categories. If you want to rely on your friend's financial support or accommodation then you will indeed need a formal invitation. Otherwise, just be upfront and truthful and it should be fine. If you are unsure about which box to check, just choose “other” and write a short explanation.