It just so happens I like cucumber salad and pickled herring, so I decided to try this combination and the results are great. You can add your own seasoning to give it some zip, but I prefer just to leave it alone. The prep time and cook time are about the same.
Combine cucumbers, tomatoes, and onion in a large glass mixing bowl.
Stir vinegar and sugar together in a small saucepan over medium-low and bring to a boil; cook and stir until the sugar dissolves. Pour over the vegetable mixture. Marinate mixture in the refrigerator for 30 minutes.
Stir the reserved liquid from the herring into the vegetable mixture. Fold herring into the vegetable mixture. Refrigerate 1 hour more before serving.