We take cheap sugar for granted these days, but back in the 18th century it was the most tremendous luxury. The Sugar Act was also called the Revenue Act because it provided increased revenues to fund enlarged British Empire responsibilities following the French and Indian War.
Being a luxury, there was a keen smuggling trade in sugar and molasses from the French and Dutch West Indies that Britain wanted to end. The earlier, Molasses Act of 1733 being ineffective, the Sugar Act aimed for strong customs enforcement of the duties on refined sugar and molasses imported into the colonies.