This is the 1543rd most frequent Polish word.
cukru
"Cukru" means "of sugar" (genitive form of "cukier").
In this sentence, 'cukru' is used in the genitive case to indicate possession or lack.
Nie mam cukru w kuchni.
I don't have sugar in the kitchen.
Here, 'cukru' is in the genitive case, as it's used with the question word 'ile' (how much), which requires the genitive.
Ile cukru potrzebujesz do ciasta?
How much sugar do you need for the cake?
'Cukru' is here in the genitive case, as it's the object of the verb 'dodaj', which requires the genitive when referring to a partitive quantity.