small can of beets (not pickled beets, just canned beets)
hard boiled eggs
slice of onion
tablespoon of sugar
(and I add cloves of garlic, too, and more onion than one slice ;-)
Get the smallest eggs you can find so more fit in the jar, if you're taking them camping, and if you want them to be snack-sized.
(That's me waving at my reflection in the jar.)
Here's a smaller jar of pickled eggs Holly made last summer. The photo links to the Just Add Light post in which it appeared.