First off Noddy, i must inform you that 'sugar pigs' are not real animals. Similarly, i too believed in santa claus but later on it was quite clear he wasn't real either. Christmas traditionally has these fun 'white lies' that make the children happy. As for the reality behind 'pigs', here's a helpful link
http://www.yourencyclopedia.net/Pig.html.
As you can see, none of them could possibly be REALLY made of sugar. You may argue that all DNA has sugar molecules in it [and phosphate, and the bases GATC] but you cannot have an entire animal made of nothing but sugars as sugars have no genetic code and reproductive methods, the least requirements to define life.