In a medium saucepan combine jalapeno peppers, cranberry juice cocktail, and vinegar. Bring to boiling; reduce heat. Cover and simmer for 10 minutes. Strain mixture through a sieve, pressing with the back of a spoon to remove all of the liquid. Measure 2 cups liquid. Discard pulp.

In a 4-quart Dutch oven or kettle combine the 2 cups strained liquid and the sugar. Bring to a full rolling boil over high heat, stirring constantly. Stir in the pectin and, if desired, hot peppers. Return to a full rolling boil; boil for 1 minute, stirring constantly. Remove from heat. Quickly skim off foam with a metal spoon.

Immediately ladle jelly into hot, sterilized half-pint canning jars, leaving 1/4-inch headspace. If using, divide the 5 hot red peppers among the 5 jars. Wipe jar rims and adjust lids. Process jars in a boiling-water canner for 5 minutes (start timing when water returns to boil). Remove jars from canner; cool on wire racks. Jelly may require 2 to 3 days to set. Makes about 5 half-pints (70 one-tablespoon servings).