sweet on (one)
Smitten with or enamored of someone. I think Samantha's getting a little sweet on her older sister's boyfriend. What about you, Tommy—anyone in school you're sweet on?
*sweet on someone
Rur. fond of someone. (Typically: be ~; become ~.) Tom is sweet on Mary. He may ask her to marry him. Mary's sweet on him, too.
sweet on
Informal Enamored of; in love with.