The phrase "is sweet on" typically implies an attraction or romantic interest in someone. Its antonyms include "dislike," "abhor," "disapprove," "detest," and "hate." These words express feelings of aversion or opposition towards the person in question. Other antonyms may include "indifference," "apathy," or "unconcerned," which suggest a lack of interest or emotional attachment. Depending on the context and tone, antonyms for "is sweet on" can also convey a sense of disgust, disdain, or disdainful amusement towards the person being discussed. Overall, these antonyms reflect a range of negative ways to describe a lack of positive relationship or romantic interest.