I expected молоко to change to молоком in the instrumental case. Can someone tell me why it changed to молока instead? Is the rule to use the instrumental case with "з" and the accusative case with "без"?
The rule is: the instrumental case with з, the genitive with без
Молоко: З молоком - без молока
Ти: З тобою - без тебе
Цукор: З цукром - без цукру
I remember having problems with that in German, but there is this song by Rammstein, Ohne rich, that helped me remember how to use mit/ohne in German:
Ohne dich kann ich nicht sein, Mit dir bin ich auch allein,
Just because German is also on your list :) Don't know of any easy way to remember that in Ukrainian.