Mix the maida, corn starch and curd to make a smooth and lump free batter. Let it rest, covered at a room temperature for 24 hours to ferment.
Next day the batter will become a little loose. Add a little maida if required to make a thick batter.
Boil the sugar with very less water to make one string sugar syrup consistency. Add half tablespoon of vinegar into it.
To make the jalebis, pour this fermented batter into a piping bag or an authentic jalebi cloth and cook the jalebis in medium hot oil. (Note that the jalebis should be cooked in a low to medium heat.)
Once the jalebis start turning brown in colour, transfer them immediately into the sugar syrup. Let them soak in the syrup for 20-30 seconds.
Serve these jalebis hot for best taste.