Combine sugar, water, ginger, lemon zest, and lemon juice together in a saucepan; bring to a boil, reduce heat to medium, and cook for 10 minutes. Cool syrup to room temperature, transfer to a container, and refrigerate until flavors blend, 8 hours to overnight.
Sift flour, baking powder, and salt together in a bowl. Rub the butter into the flour mixture with your fingertips until mixture has a cornmeal texture. Add the milk; mix until a smooth dough forms. Wrap the dough in plastic wrap and let it rest for 2 hours.
Turn the dough out onto a lightly floured work surface and roll into a 5x14-inch rectangle about 1/4-inch thick. Cut the dough into twenty eight 1/2-inch wide strips. Twist pairs of strips together and pinch the ends together. Repeat for all of the strips. Cover strips with a clean cloth and let rest for 15 minutes.
Heat about 2-inches of oil in a deep-fryer or large saucepan to 350 degrees F (175 degrees C). Place a wire rack over a baking sheet.
Pour some of the cold syrup into a bowl and return remaining syrup to the refrigerator.
Working in batches, fry koeksister twists in hot oil until twists swell and are golden brown, 2 to 5 minutes. Remove koeksisters from hot oil with a slotted spoon and immediately immerse in cold syrup for 10 seconds. Transfer soaked koeksisters to prepared wire rack to cool. Replenish cold syrup as necessary.
We have determined the nutritional value of oil for frying based on a retention value of 10% after cooking. The exact amount will vary depending on cooking time and temperature, ingredient density, and the specific type of oil used.