Hard boil quail eggs in a small saucepan. Peel and set aside to cool. In the meantime, bring 1 part vinegar to 1 part water to the boil and add 2 tbsp of salt and 2 tbsp of sugar. At this point, you can also add different spices into the mixture, such as caraway seeds, paprika, saffron, cumin and/or coriander seeds. Place the quail eggs and the mixture into a glass jar and place in the fridge overnight.