Tree sap can be one tough contaminant to remove from your car's finish. If not done properly you can leave your finish damaged and paint scratched. There are a couple ways you can treat tree sap.
If the sap has recently fallen and not hardened, you can apply Eco Touch All Purpose Cleaner and gently dab off. Remember not to apply too much pressure. If you aggressively rub you will end up marring the vehicle paint.
If there is hardened sap you'll need to move onto a stronger solvent. Although not 'green' we've found that minerals spirits is your best bet for dissolving the spots. Again, gently dap the spot with mineral spirits and wipe off with a microfiber towel.
Now that the sap has been removed you'll need to apply a paint polish and re-coat the surface with a wax.