Look for home remedies on the net. Just about anything oil based will soften and dilute sap.
I'd stay away from chemicals as much as possible - and test in a hidden spot.
Quick Google search:
# Apply nail polish remover with a cotton ball or swab and rub gently until the sap is removed.
# Buff lard onto the area with sap and wipe with a lint free cloth, such as a cloth diaper or terrycloth towel.
# Avon's Skin So Soft bath oil is also said to be an effective sap removal agent. Rub it onto the sticky area and wipe clean with a cloth.
# Try dabbing the area with a cotton ball moistened with rubbing alcohol.
# Remove sap from your automobile by applying bacon grease and wiping clean.
# Make a paste of baking soda and water and use to clean your car. Wipe clean with a damp cloth.
# Mineral spirits mixed with denatured alcohol will remove sap without ruining your auto's paint job.
# It may sound funny, but polishing your car with mayonnaise will also remove sap.