Keep a canning jar ready by washing the jar and lid well and sterilizing it in hot water or in the oven. (please see in my notes below for jar suggestion)
Wash your jalapeños well and cut off the stem. Slice your peppers.
12 ounces Jalapeno Peppers
Now grab your jar. At this point, you can add in whole spices if you like to add flavor to your pickled jalapeños.
Pickling Spices
Place your jalapeño slices into the jar.
Heat up a saucepan to create the pickling brine with the vinegar, water, salt, and sugar. Mix well and bring to a light boil.
1 cup Vinegar, 1 cup Water, 2 Tablespoons Salt, 2 Tablespoons Sugar
Pour the hot brine over the jalapeños in the jar. Make sure all your pepper slices are covered by the brine.
Close your jar and leave your pickle out at room temperature for 2–3 days. Test after two days if your pickle is ready to be refrigerated. It should taste like a pickle.
Store in the fridge until further use.
Video
Notes
You have the option of adding pickling spices. I like to add a combination of mustard seeds (yellow or brown), black/green/pink peppercorn, caraway seeds, fresh garlic sliced and allspice berries. Add as much as you like to your jar before placing the sliced raw jalapeños into the jar.
Use a Vinegar with 5% acidity. If it's a stronger vinegar, add some more water to even it out, and if it's a lighter vinegar, add more vinegar than water.
Keep around 2–3 days out at room temperature before refrigerating so that the jalapeños take in the flavors and get properly preserved in the brine.
Refrigerate after 3 days for up to 1–2 months. They are usually not that good anymore when they are soggy and soft.
For the Jar, I use Italian ¾ liter Bormioli Rocco Jars which come with a rubber. Those are of great quality and perfect for canning jalapeños. I wholeheartedly recommend you get these thick, high-quality glass jars for your homemade pickles.