"Mom makes juice."
Translation:Мама делает сок.
Be careful! «Сока» is not in the nominative form. The nominative form is «сок», and since it’s a non-animate masculine noun in the singular form (complicated but essential to know) it will remain «сок» in the nominative form; therefore, it is: «Мама делает сок». «Соку», the word you’ve mentioned, isn’t an incorrect word, but it’s in the dative form, and you’ll know more about that in further lessons.