I seen several times the claim than sugar was an essential nutrient for industrial revolution workers (for example this blog) and even that sugar availability made possible the industrial revolution, at least in Britain.
My (maybe wrong) understanding of these claims is that sugar became a sort of staple food for British workers. However, I can't imagine people having a bowl of sugar for lunch but I suppose a diet made mostly of bread, potatoes, vegetables and occasionally a little meat, with sweet food being mostly deserts or snacks, and even then those sweet foods are mostly composed of ingredients other than sugar, like flour. Therefore, I can't see where a large quantity of sugar fits in an industrial revolution worker diet.
Is it true that industrial revolution British working class families consumed large quantities of sugar? How did they consume it?
According to the book linked in Brian Z's answer (Syndney Mintz's classic book Sweetness and Power, chapter "Consumption", p. 149) before 1850 sugar have been mostly a sweetener for tea which added very few calories to worker's diet, but after 1850 "it appeared not only in tea and cereal but in many other foods as well and in ever-larger quantities" and it was contributing to one-sixth or per-capita caloric intake.
1/6 of daily caloric intake is 1/6 of 2000 to 2500 kcal, that is about 400 kcal, and that's a bit more than the calories in 100g sugar, which is an amount better measured with a teacup than in teaspoons.
Then the question is what the "many other foods" containing sugar that labouring families ate daily were.