There is a recommended upper limit, your comment makes it sound like sugar is a requirement. I think some people might still believe you "need" sugar, I certainly grew up with that notion.
Sugar is one of the possible ways of getting carbohydrates, certainly one of the most delicious.
You won't get sick if you get your carbohydrates from some non sucrose / fructose source.
And certainly one of the most expensive ones in the long run.
Sugars plural yes
Hypoglycemia