Watkins will support Sweet Charity president and Booker CEO Charles Wilson, succeeding him as president when he steps down next September.
"It is a great honour," Watkins said. "I have always been a big supporter of the work done by Sweet Charity and hope, alongside Charles Wilson, I can play a part in raising much-needed funds.
"Sweet Charity helped over 1,500 people last year, Like most, I am aware that times are difficult, but if we work together as an industry, I am sure we can continue to support this worthy cause."
Watkins has worked at Mars for 10 years in a number of roles including general manager of the ice cream business and transformation director for the UK chocolate business.