This is not a year of eating sandwiches. Rather, it is the opportunity to gain work experience as a part of your undergraduate degree program in the UK. It is called a "sandwich year" because it is sandwiched between the second and third year of an undergraduate degree program.
British universities are leading the way with opportunities such as these because they place such a strong emphasis on employability as a part of their degree programs. American students can take advantage of sandwich years for less time and money than if they remained in the US for their studies. If you'd like more information on sandwich courses and work experience in the UK, please do get in touch with Across the Pond.