Remove the husks from the tomatillos. Wash the fruit well in cold water. Cut the tomatillos in half and remove the cores. Chop tomatillos and measure about 4 cups.
Wear plastic or rubber gloves when chopping and seeding fresh jalapeño peppers. (The gloves will protect your skin from oils in the peppers that can burn your skin and eyes. If your skin should touch the peppers, wash the area well with soap and water.)
Remove stems from the peppers and then cut the peppers in quarters. Use a paring knife to scrape out the seeds. Chop finely. You should have 1/4 to 1/3 cup.
Combine tomatillos, apples, sweet pepper, vinegar, jalapeño peppers, cilantro, sugar, and salt in a 4- to 6-quart kettle. Bring to boiling. Reduce heat and simmer, uncovered, for 15 minutes.
To fill the jars, place a wide-mouth funnel in a clean, hot half-pint canning jar. Ladle salsa into hot jars, leaving 1/2-inch of space at the top of the jar. Remove the funnel and wipe the jar rim with a clean, damp cloth. Any traces of food left on the rim prevents a perfect seal. Position a prepared lid and screw band, tightening according to manufacturer's instructions. Set each jar into boiling water in a water-bath canner as it is filled; jars should not touch one another. Cover the canner. Begin the processing time when water returns to boiling. Process for 10 minutes in a water-bath canner. Remove from canner and cool on racks.