I have been on the receiving end of an unexpected gift. Actually I was in a restaurant and the owner (who knows I am learning Cantonese/Mandarin), just gives me some dong gua tong (soup). I didn't order it and the situation made me wonder what is the appropriate phrases for receiving unexpected gifts. I recall that in Cantonese one can say doh je! instead of m goy (or m goy sai) and I think in Mandarin xie xie might suffice but I'd like to ask what other appropriate phrases exists?
I am sure many variations may work but I'd appreciate some more insight if there are phrases which might be more appropriate than others.