My Mom always made something like this:
CUCUMBER SALAD
3 medium cucumbers, thinly sliced
1 medium sweet onion, sliced thin and separated into rings
1 cup white vinegar
1/4 cup vegetable oil
1 cup water
1/4 cup sugar, or more to taste (or diet sweetener)
The cucumbers may be scored or part of the skin can be peeled for better absorption of the juice.
Layer cucumbers with the onion in a large bowl. In a separate bowl, mix remaining ingredients, stirring until sugar has dissolved.
Taste and adjust sugar for sweetness, adding more sugar, if needed. Pour over vegetables and toss lightly.
Cover and chill for 2-4 hours before serving.