Believe it or not, WD40 will work on tree sap.
Spray the affected area with WD40, let it sit for about 10-15 mins. After it has soaked in, use a microfiber towel and wipe the area with some medium pressure. Apply more WD40 to the area as you are wiping. The sap will dissolve and be removed. The WD40 will not affect the clearcoat nor will it strip or damage any painted surfaces. After removing sap, rinse or wash car - reapply wax to area (if applicable).
WD40 can be used to remove most sticky residues on vehicles. It is also good to spray under the hood on metal engine components to prevent rusting and oxidation (such as aluminum brackets, bare metal engine parts, etc). This is great for vehicles that sit outside for long periods of time, as well as those that may be stored. The WD40 will not burn or catch fire if engine is started and operated. It is also great to repel dirt/debris because once applied, rinsing the engine bay later on will produce great results!
Been using WD40 in that manner for years now on my prior and current Mustang(s), prior Bronco(s), Jeep, and man other vehicles.... Never an issue.