(as) sweet as sugar
Exceptionally sweet, friendly, or kindly. My grandmother, God rest her soul, was as sweet as sugar, but boy could she tell some raunchy jokes! He may seem sweet as sugar right now, but he'll turn on you in an instant if you get in his way. Katie is just sweet as sugar and goes out of her way to befriend the new kids in school.
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.