Yeah but fast food, sugar etc are light/very light drugs and there is work in progress to limit them(i.e the amount of sugar in snacks etc).

Sugar is not "lighter" than, for example, cocaine.

Sugar related health issues such as diabetes and obesity have far higher costs to society than cocaine abuse does.

I believe cocaine is more addictive than sugar. Cardiac arrest is another issue. Not much is known about long term health effects of cocaine because we don't have a majority of population snorting cocaine and eating and drinking it every single day.

you need to correct for per-user cost, i.e. cost per user of sugar vs per user of coke