One recipe that includes cucumber, onion, vinegar and water as ingredients is cucumber and onion salad. There are two versions of this recipe, each with a slight variation on the ingredients used.
To make one version of cucumber and onion salad, cut the ends from 2 to 3 large cucumbers, and peel the cucumbers partially, leaving three to four strips of skin intact. Slice the cucumbers into rounds.
Peel and slice 1 medium white onion into thin slices. Separate the slices. Place the cucumber and the onion in alternating layers inside a 2-quart jar. Add 1 cup white vinegar, 2 cups water, 1 tablespoon pepper and salt to taste. Place the lid on the jar, and turn the jar to mix the ingredients together. Refrigerate the jar overnight. Serve the salad cold.
To make a similar salad, peel and thinly slice 2 cucumbers and 1 large red onion, and place them in a heat-proof serving container. In a saucepan, combine 1/3 cup each of sugar and cider vinegar, 3 whole cloves, 2 teaspoons of salt and 1 teaspoon of pepper. Bring the mixture to a boil over medium heat. Stir to dissolve the sugar, and then reduce the heat to low, cover the saucepan, and cook for five minutes.
Pour the vinegar mix over the onions and cucumbers in the bowl, stirring to mix. Cover the bowl, and refrigerate it for two hours prior to serving.