Add enough water so that all the berries are submerged.
Cover well (I love these reCAP mason jar lids, they can be used with a waterless fermenter).
Keep at room temperature for 2 weeks.
Transfer to refrigerator after 2 weeks. Lingonberries can now be eaten, although I think the flavor improves with longer storage.
Notes
The berries will eventually come to float, which is fine. There is no need to weigh them down. I like to eat brined lingonberries with savory dishes and tossed with sauerkraut.
I love them with beef goulash and mashed potatoes! All my kids enjoy them but my 22-month old is completely obsessed with them, it's pretty funny to watch.
Back in Russia, some folks mix brined lingonberries with honey or sugar before serving them like a sauce.