Crockpot Corned Beef & Cabbage

1 (4 ½ pound) corned beef brisket
2 medium onions, quartered
½ teaspoon pepper
3 Tablespoons vinegar
3 Tablespoons granulated sugar
Potatoes (optional)
Carrots (optional)
1 cabbage head, cut into small wedges
2 cups water

Combine ingredients in crockpot with the cabbage on top. Cut meat to fit, if necessary. Cover and cook on low 10-12 hours or on high 6 to 7 hours or according to your crockpot cooking recommendations.