Place 4 mason jars in canning pot, fill with water and bring to a boil.
In a separate large pot, pour, vinegar, water, salt and sugar in and stir. Bring to boil.
Meanwhile, wash jalapenos and slice of the tops.
Slice jalapenos into small rounds about ⅛ inch thick. Set aside
When brine comes to a boil, stir and allow to boil for 3 minutes. Turn heat to low.
When jars are boiled, remove jars one at a time and fill with jalapeno slices. Fill to just below neck of jar. Do not pack them, they should be touching but not packed in.
Ladle brine into the jar, covering the slices completely.
Place lid and ring on jar.
Continue with next jar, working with one jar at a time until they are all filled.
Place filled, capped jars back in canning pot and bring back to a boil. Make sure there is enough water in the pot to cover the jars completely and have another inch or so of water above the top of the jars.
Allow water to boil for 20 minutes.
Once boiled for 20 minutes, turn off heat and allow water to cool with jars in it for 30 minutes.
Remove jars from water and dry them. Turn jars upside down for 10 minutes on a tea towel.
Turn right side up and allow to sit at room temperature for 24 hours.
After 24 hours, check lids to make sure they sealed. Press down lightly on lid and if it springs back, it did not seal properly. Any jars that did not seal should be placed in the fridge.
All properly sealed jars can be stored at room temperature for another 13 days before serving.
Once opened, store in fridge for up to 3 months.