Try HOT soapy water on a small rag. Let it sit/soak for a minute then wipe away with a dry soft cloth. Repeat again if necessary. The hotter the better as the heat literally thins & melts away tree sap. My wife's black 330i gets covered in pine sap all the time and it works like a charm with no residual swirls or scratches at all. Just remove the sap quickly and don't let it sit on the finish for days on end. If you do, don't be surprised to see the clear coat being lightly damaged by the resins in the sap. Just my 2 cents...