sorrento to siena

The easiest may not be the cheapest but here goes. Sorrento to Naples Centrale by the private Circumvesuviana train. These are Regionale trains. About 4E. At the station, go upstairs to the Trenitalia part of the station. You can take a high-speed from Naples to Florence with no train changes. At Florence you change to a Regionale train for the ride to Siena. At Siena, you will most likely need a taxi to get to your hotel from the train station as the station is about a mile slightly downhill from the city. Ordinary fare for this ride is 79.70Euro. Journey time is just under 5hrs. You can reduce the fare by carefully selecting less expensive and slower trains. If you need assistance in doing this, just ask.