Sort out the raspberries. (You should not wash them!)
Put the berries with the apple cider vinegar in a wide-mouthed jar, close it tightly and put it in the dark for two weeks.
Shake the jar once a day: This is very important so that no berries can lift out of the top of the vinegar and spoil!
Run the finished vinegar through coffee filters and pour into bottles (preferably old vinegar bottles).