Divide the green beans, onion slices, and jalapeno slices between two pint-sized mason jars. Try to get an even mix of jalapeno and onions in both jars.
Make the Brine
In a small saucepan, combine the brine ingredients. Bring to a boil, then remove from the heat.
Ladle the hot brine over the green beans mixture in the jars. When they're cool enough to handle, refrigerate until you're ready to serve.
Video
Notes
For dilly beans, stir a handful of fresh dill into the brine after boiling.These taste best if you chill them for 24 hours before serving, but you can technically eat them the second they're cool enough to handle.Once they're cool enough to handle, close your jars and place them in the refrigerator. They will keep for up to 3 weeks.