Rinse the green chillies and pat them dry.
Slice them into rounds. Remove the seeds if you don't want them to be hot.
In a pot, combine the vinegar, salt, and sugar.
Heat the mixture until the sugar and salt are dissolved.
Place the sliced green chillies in a clean, sterilized jar.
Pour the hot vinegar mixture over the chillies, ensuring they're completely submerged.
Seal the lid and allow the jar to cool at room temperature.
Once cooled, put it in the refrigerator. They'll be ready to enjoy after 24 hours.