Learn Turkish: Lezzetli tatlıları doyasıya yedik. - We ate the delicious desserts to our heart's content.

doyasıya comes from the verb root doy- (to become full, to be satisfied) plus the converb suffix -asıya. This suffix expresses an extreme limit or doing an action to the absolute maximum. Here, doing something "until completely satisfied" translates perfectly to the English idiom "to one's heart's content."

Could we use doyana kadar instead of doyasıya?

Yes, you could say doyana kadar yedik (we ate until we were full). However, the -(y)AsIyA suffix in doyasıya carries a stronger emotional nuance of extreme enjoyment or indulging without holding back. It feels less like a strict physical limit and more about reaching a state of ultimate satisfaction.

Why is it tatlıları rather than just tatlılar?

The accusative case suffix -ı on tatlıları (tatlı-lar-ı) shows that it is a specific direct object. You are saying "we ate the delicious desserts" (referring to specific desserts, perhaps at a party or restaurant), rather than just eating delicious desserts in general.

Is doyasıya only used with eating or drinking?