The antonyms for the phrase "were sweet on" depends on the context in which it is being used. If it refers to romantic attraction, antonyms could be dislike, hatred, loathe, detest, or repulse. Alternatively, if it has a connotation of being fixated on something, antonyms could be indifferent, uninterested, apathetic, or unconcerned. The phrase "were sweet on" typically implies a positive or pleasant feeling towards someone or something, so the antonyms would be words that indicate a lack of interest or a negative feeling. It is important to consider the context in which the phrase is being used to determine appropriate antonyms for it.