Stir yeast and sugar into the water. Mix together water, yeast and sugar, let it sit for few minutes until all yeast is dissolved.
Combine salt and 1 cup of flour in a mixing bowl, then make a well in the middle and add water mixture. Mix in liquid into the flour, it will turn into thin batter. Cover with cloth and let sit for 30 minutes.
I used my Kitchen Aid mixer, gradually stir in remaining flour. Dough should turn out soft. Knead until smooth and elastic.
Cover again. Let it sit for about an hour, until doubles in size.
Place dough on floured surface, stretch it into a long log. Divide log into 20 even pieces.
With your finger, punch out hole in the middle. Shape of the donut doesn’t have to be perfect, they will puff out in the oil.
Heat oil until its sizzling, keep heat on medium low so when you drop donut inside it would burn right away. Drop donuts one by one into the oil, cook until golden on each side.
Lift them with skewer, drain on paper towels. Toss donuts in sugar when they are still warm.