Slice jalapeños in half lengthwise (or quarter depending on size of peppers) or slice into thick rounds. Remove seeds if desired for a little less heat. Divide sliced jalapeños between 4 clean, sterilized 1-pint canning jars, leaving about 1/4 inch room at the top of the jar. Trim stems from cilantro and divide the bunch to pack some into each jar. Combine water, vinegar, and salt in a large pot and bring to a boil, stirring to dissolve salt. Divide garlic, bay leaves, coriander seeds, and your choice of peppercorns, mustard seeds, and aromatic seeds into each of the 4 jars. Pour the hot vinegar mixture into each jar to cover jalapeños, leaving about 1/4 inch room at the top of the jar.
For a refrigerator pickle: Seal and let cool to room temperature before refrigerating. Best after 1 week; enjoy within a couple of months.
To can: Seal with a 2-part canning lid and process in boiling water (with jars covered by water) for 10 min. Let cool to room temperature and make sure lids are sealed; lids shouldn’t bounce back when pressed. Refrigerate any jars that didn’t seal; otherwise, store in pantry and let sit for at least 1 week before enjoying. Use within 1 year and refrigerate after opening.