When someone has a crush on another person, they may say they are "sweet on" them. However, there are many other phrases and synonyms that can be used to describe this feeling. Some similar phrases include "infatuated with," "smitten with," "enchanted with," and "charmed by." Other synonyms for "sweet on" could be "fond of," "having a soft spot for," "attracted to," or "taken with." Depending on the tone and context of the conversation, different words may be more appropriate or effective in capturing the level of affection and interest someone has for another person.