In a large mixing bowl, combine the flour, baking powder, salt, and sugar (if using).
Add the vegetable oil or melted butter to the dry ingredients.
Gradually add the water, mixing until a soft dough forms. If the dough is too dry, add a little more water, a tablespoon at a time.
Transfer the dough to a lightly floured surface and knead for about 5 minutes until it becomes smooth and elastic.
Cover the dough with a damp cloth and let it rest for about 30 minutes.
After the dough has rested, divide it into 8-10 equal portions.
Roll each portion into a ball, then flatten and roll out each ball into a circle about 1/4 inch thick.
Cut each circle into quarters to form triangles.
In a large skillet, heat about 1 inch of vegetable oil over medium-high heat until it reaches 350°F (175°C).
Carefully place a few dough triangles into the hot oil, being careful not to overcrowd the skillet.
Fry the dough for about 1-2 minutes on each side, or until they are golden brown and puffed up.
Remove the fry jacks from the oil and place them on paper towels to drain any excess oil.
Enjoy your meal!