"The bear drinks the beer."
Translation:Ayı birayı içer.
I think... iç is the root of the verb to drink (içmek) içer is the conjugation of he/she/it drinks. root + (e or a) + r
'e or a' depends on which is the final vowel sound in the root (in this case it is 'i'). This is also why the infinitive 'to drink' is içmek and not içmak.
It has to be ayı because it is the subject. To have the -yı suffix added, it would need to be both definite and the direct object of the sentence.
Ayı gördüm. = I saw a bear / bears. [indefinite object]
Ayıyı gördüm. = I saw the bear. [definite object]
Ayı beni gördüm. = The bear saw me. [definite subject]