The fastest way to reach Machu Picchu is by train, and this option is ideal for people who do not have the time to, or do not wish to, hike one of the trails. There are no roads that reach Aguas Calientes, and the train is a lovely option.
The railway between the Sacred Valley and Aguas Calientes runs alongside the Urubamba River cut into the mountain sides. There are various class options, from the basic ticket right up to the Hiram Bingham luxury ride that is accompanied by food, drink and entertainment.
Machu Picchu by train 2d/1n
To ensure having ample time to visit Machu Picchu, a two day trip is recommended. This option will bring you to Aguas Calientes on day 1, where you will have time to explore the town, enjoy the hot springs, and eat out at one of the many restaurants. We recommend an early night so that you can wake up bright and early for the ascent. If you wish to reach the entrance to Machu Picchu for when it opens, you will need to hike for about an hour uphill. Alternatively, buses depart frequently for the summit. You will enjoy a 2 hour guided visit of the site, with time afterwards to explore on your own, and perhaps climb Huayna Picchu or Machu Picchu Mountain (tickets required). In the afternoon you will return to the Sacred Valley by train, and transported to Cusco by car/van.
Machu Picchu by train 1 day
If your schedule is very tight you might consider this option. You will travel to and from Cusco by car and then train, and immediately ascend from Aguas Calientes to Machu Picchu by bus. Your guide will give you a tour of the site, and there will be some time to explore before returning to Aguas Calientes. You can opt to take the late train back to the Sacred Valley so that you have some time to eat dinner in Aguas Calientes.