This is a hard question on the one hand in theory it could help decrease the number of sugar addicts as people would turn to healthier options. I know 11 year old sarah who would spend all her pocket money on sweets probably would be saved as she could no longer afford these treats and she may not be in the mess she is in now.
But
If the government taxes sugar hevily it means that their income will become based on the sugar andjunk food industry. This would make it harder to eliminate the problem that is sugar addiction as the govermnent would do everything in its power to insure that junk food exists so they can keep their revenue. A good example of this is the tobacco industry. Everyone knows tobacco is bad for us and that it is also highly addictive but the government heavily taxes it and so although they on the surphace appear to be trying to combat the smoking problem they have never tried to remove it completely.
I could go into the benefits of taxing for the nhs but I thought it best not to be region specific.