Fry bacon until crisp.
Remove crisp bacon pieces.
To the bacon fat, add vinegar, water, and sugar, and bring mixture to a boil.
Place lettuce or spinach, torn into bite-size pieces, in a salad bowl.
Top with onion rings and hard-cooked eggs.
Pour hot vinegar mixture over salad and toss until well mixed.
Sprinkle reserved bacon pieces over the top.