Add enough oil to a large saucepan or deep skillet to come to a depth of at least 2 inches; heat to about 350 degrees.
Mix 1/2-cup sugar and the cinnamon together on a large plate.
Combine remaining sugar, butter, salt and 1-cup water in a saucepan over high heat, and bring to a boil.
Turn heat to low, and add flour, all at once.
Stir constantly until mixture forms a ball, about 30 seconds.
Remove from heat, and beat eggs one at a time into mixture, stirring until smooth after each addition and spoon dough into a pastry bag with a large star tip.
Press strips of dough about 4 inches long into hot oil.
Cook as many as will fit comfortably at once, turning as they brown, 5-10 minutes each.
Remove churros from oil, and drain on paper towels, then immediately roll them in cinnamon-sugar mixture.
Serve hot or warm.