KOBLIHA is the right answer. In THE SIMPSONS is it also translated as KOBLIHA. But kobliha is only similar to donut, not really the same, but the word kobliha is used also for donut and also for that czech kind of donuts. You can use also the word DONUTKY (plural) (read dońootkee) - it is not often used, but it is more correct for real donuts (but never used with that czech version of donuts).