Pickling this cabbage gives you a fresh twist on sauerkraut.
In a large heatproof bowl, combine cabbage, cucumber, and onion.
In a medium saucepan, combine 1 1/2 cups water, vinegar, sugar, and salt; bring to a boil, stirring to dissolve salt and sugar. Immediately pour over vegetables; using a dinner plate, press down on vegetables until they are submerged.
Let cool to room temperature; transfer vegetables and liquid to an airtight container, and refrigerate up to 2 weeks. Use as you would sauerkraut or pickles, such as in Open-Face Ham Reuben Sandwiches.