Green’s Dictionary of Slang

sweet adv.¹

amorously.

1865		Leaves from Diary of Celebrated Burglar 24/2: We had only been two days in the place when she began to look ‘sweet’ on one of Joe’s (Fobb’s) ‘pals,’ and ditto on his side.
1877		‘’Arry on His ’Oliday’ in Punch 13 Oct. 160/2: I looked sweet / On a tidy young parcel in pink as ’ung out in the very same street.