sugar the pill
Make something unpleasant more palatable, as in There would be no Christmas bonus this year but management sugared the pill by giving workers extra vacation time over the holidays. [Late 1700s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.