When the marinade starts to boil, put the donuts and eggplants in proportional quantities, until you fill the pan. I have a 5 liter pan, and I put the donuts in 3 rounds. After the first round boils, take out the donuts, put them in jars, then put the next ones.
When the donuts start to boil, turn down the heat and leave for 5-7 minutes, don't forget to stir.