He drinks your milk.hu: Megissza a tejed.
Duolingo forum topic: https://forum.duolingo.com/comment/1784119
I recommend reading the Tips and Notes for the last skill in the Hungarian course.
I copy it here:
Here, you will meet possessed direct objects, objects with both a possessive and an accusative suffix. The form is that the noun is followed by the possessive marker and by the accusative marker - in that order:
• ház → ház-am → ház-am-at ‘my house (obj.)’
The accusative is fairly regular, too. Recall that for a word like alma ‘apple’, adding the accusative lengthens the final vowel:
• alma → almá-t ‘apple (obj.)’
The same happens with possessive forms ending in -a:
• ház-a ‘his/her/its house’ → ház-á-t ‘his/her/its house (obj.)’
Note that possessed direct objects (nearly) always require the definite verb form, and they often appear with a definite determiner or possessor .
Finally, if the possessor is in the first or second person singular, the accusative can sometimes be omitted:
• Add a kezed! ‘Give me your hand!’
Here, it is fairly common to just use kezed instead of kezedet. But if the possessor is in the third person this is never possible.