Not normally a sweetie person myself, but a friend shared some Marks and Spencers sugar free butterscotch sweets with me and they were *lovely* - (a hard, sucking sweet) - they come in a cigarette pack sized cardboard flip top box.
I looked them up when I got home, and although I can't quite remember, the whole packet came to about 4 or 5 syns, so one or two would 'cost' very little, and really take the edge of a sweetie craving ..