You could try a tar and glue remover but as it's on the bonnet and roof I wouldn't spray or poor it on, I would poor a little on a rag and put it on top of the sap for no more than a few minutes. Once it's been soaked for a minute or two gently rub it with the cloth, you may need a few goes at it but it should work. Once it's off wash the area and rinse thoroughly, the problem with sap is that if left for any length of time it can end up etching the lacquer and/or paint !