I take 150 ml of water and add a heaping teaspoon of boric acid and add 70 to 80 ml of clear vinegar to it. Then I pour it into those containers which have isopropyl alcohol sheets (can buy them in drug stores or Kmart or Walmart).
I pull out a sheet, squeeze out excess fluid and wipe out my dogs ears with it. Boric acid and vinegar kill bacteria and fungus. Boric acid can also kill ear mites.