In a large bowl, mix together the flour, yeast, sugar, and salt. Gradually add water and mix until a dough forms.
Knead the dough on a lightly floured surface until smooth and elastic, about 10 minutes.
Cover the dough with a damp cloth and let it rest for 1.5 hours, or until it doubles in size.
On a lightly floured surface, roll out the dough into a rectangle about ½ inch thick. Cut the dough into strips, then lay one strip on top of another and press them together lightly with a chopstick.
Heat oil in a deep fryer or large pan to 350°F (175°C). Fry the dough strips until they are golden brown and puffed up, about 2 minutes on each side.
Remove the youtiao with a slotted spoon and drain on paper towels.
Serve warm as desired.
Notes
Knead the dough until smooth and elastic for the best texture.
• Let the dough rest adequately to ensure it's easy to shape and fry.
• Roll the dough evenly for uniform cooking.
• Fry at a consistent medium-high heat to achieve a golden brown exterior and soft interior.
• Place fried youtiao on paper towels to absorb excess oil.