Burnet vinegar has the taste of cucumber to it from using the herb called salad burnet.
5 tablespoons of chopped fresh salad burnet
3/4 cup (6 oz / 175 ml) white wine vinegar
Well in advance: wash the salad burnet leaves, shake and pat dry, then let stand for all the water to dry off them completely, an hour or two (or you may get white sediment.) Sterilize your jar or bottle. Bring the white wine vinegar to a simmer. Remove from heat, add the leaves, stir the leaves and squish them. Pour into your jar or bottle. Let cool, then seal. .Let stand in a dark place at room temperature for 2 weeks, shaking from time to time, then filter into another bottle.
You can also make it used dried salad burnet seed, which has been crushed.