Questions & Answers about El azucarero está vacío; luego compraré más azúcar.
Because they are doing two different jobs in the sentence:
- el azucarero = a specific, known object: the sugar bowl
- más azúcar = an amount of a substance: more sugar
Spanish often uses the definite article with a specific object, just like English:
- el azucarero = the sugar bowl
But with an uncountable substance after más, no article is needed:
- más azúcar = more sugar
So the sentence is talking about:
- a specific container that is empty, and
- buying a greater quantity of sugar later.