Why the variant יש לזה סוכר? Is not accepted?
That would mean "Does it have sugar?"
why is there no ל in front of it?
When using the word יש to mean "has", the ל goes in front of the person who has something, for example:
The woman has sugar - יש לאישה סוכר.
When יש is used without the ל, it isn't specified who has the object and it just means "There is ___".