Mayor Michael Bloomberg's administration plans to keep tightly under wraps any potential changes to a controversial proposal to restrict the sale of large-sugary drinks in New York City until the day of the Board of Health's vote next month, the city's health commissioner said Wednesday.

As the Journal reported, Bloomberg sparked criticism on Tuesday when he said the administration didn't have any suggested alterations – substantial or slight – to the proposal following months of public debate. In May, the mayor recommended...