sugar
The Italian word for sugar is 'zucchero'. It is used in the same way as in English, to refer to the sweet, crystalline substance that is added to food and drinks. It is also used in the same way as in English to refer to sweetness or endearment. For example, you can say 'dolce come lo zucchero' which means 'sweet as sugar'.
I like coffee with sugar.
This sentence is a simple statement which expresses a preference for drinking coffee sweetened with sugar.
Where is the sugar?
This is a question that someone might ask if they are looking for sugar, perhaps in a kitchen or a grocery store.
Sugar is sweet.
This statement is a basic fact asserting the sweetness of sugar.