Cucumber salad is not affiliated with any Jewish holiday, but when planning a full dinner, vegetables are very important.  Cucumbers are inexpensive, the salad compliments many meat dishes, and the vinegar in the marinade helps clear the palate.
2 large cucumbers peeled and seeded.
1 large onion, (cut into thin slices or chop in small pieces)
Cut peeled and seeded cucumbers into strips of desired lengths,
approximately 1 to 2 inches long. 

Place the cucumbers and onions in a flat bottomed bowl or casserole dish.  
Pour marinade over them and place in the refrigerator to chill.
1/4 cup rice vinegar
3 Tbsps. water
2 Tbsps. sugar or 1 packet sugar substitute
1 tsp. salt

*Note: Also, adding fresh chopped tomatoes to the cucumbers and a few sprinkles
of your favorite spices or fresh parsley really spices up this salad.