It'll be 1 syn per 20 calories as pre-made soup doesnt qualify for free food allowance. So according to their website that's 2.25 syns per 100g so about 9 or 9.5 syns a tin.
Some soups are but I cant go through the whole list to find out sorry Even if it was it probably wouldnt be the whole tin though, its usually only about 200g - 300g (about 6 syns worth)