Below is a recipe that asks for 1 cup of sugar I'd guess you folks can
work around that.

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Pickled Herring
Recipe courtesy Tyler Florence
Show: Food 911 Episode: The Swedish Chef


Recipe Summary

Yield: 6 servings


3 to 4 whole salted herrings
2 cups milk
1 1/2 cups water
1 cup white sugar
1 cup white vinegar
2 teaspoons ground allspice
2 teaspoons yellow mustard seeds
1 teaspoon caraway seeds
2 teaspoons whole black peppercorns
2 teaspoons whole white peppercorns
1 small red onion, sliced in rings
2 carrots, cut in thin slices
2 handfuls fresh dill
2 bay leaves
2-inch piece fresh horseradish, cut in big slices

Soak the herring in the milk for at least 12 hours or up to 24 to draw
out a lot of the excess salt. Drain the herring, rinse, and pat dry. Cut
off the fins and fillet the herring, leaving the skin on. Cut the
fillets crosswise into 2-inch strips.

In a saucepan, combine the water, sugar, vinegar, allspice, mustard
seeds, caraway seeds, and peppercorns. Bring the mixture to a boil,
stirring to dissolve the sugar. Remove from the heat and cool the
pickling mixture completely.

Arrange the herring fillets, onion, carrots, dill, bay leaves, and
horseradish in a glass dish or funky Mason jar. Pour the cooled pickling
mixture into the jar so that all the ingredients are completely covered
with the liquid. Cover and refrigerate overnight or up to 2 days before
serving.

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We purchase herring in mustard sauce and vinagar often. The Vinegar
tidbits are washed and refreshed with new vinegar and onion. I'd hazard
a guess the sugar is reduced by the refreshing aspect.

--
Bill Garden in shade zone 5 S Jersey USA