First, cook the brine: In a pot, combine water, sugar, salt, bay leaves, allspice, and black pepper. Bring to a boil, lower the heat and simmer for about three minutes, until everything comes together. Remove from the heat and let the hot vinegar mixture cool almost wholly; the brine may be lukewarm but not hot.
In the meantime, start preparing the sausages. Peel off a thin layer of the casing and cut them lengthwise, but do not finish the cut. The sausages should open up enough to insert the onion rings and peppercorns into the cut.
Peel the onion, and cut lengthwise. Then thick-slice the halves of onions into half-rounds.
Clean the hot chili peppers, cut off the stem part, and cut them in half lengthwise. Remove the seeds, or leave them if you want a spicier result.
Carefully open the sausages. Insert a piece of hot pepper and onion rings into the cut.
Prepare a two-quart glass bottle (2 liters), such as a jar with a screw cap or clip-on lid. Wash the jar properly with hot water and dry it.
Place onions in the bottom of the jar, then start putting the filled sausages on them. Gradually pour the brine over sausages and add some onions between each layer. Stuff the sausages into the jar to avoid unnecessary gaps in-between.
Cover the top with the rest of the onions and pour in the brine to submerge the sausages, including the onions.
Close the jar with a lid and put it in a fridge to mature. Let the pickled sausages sit in the refrigerator for at least a week, preferably two, before you dig in.