I've only tried ACV & water twice & both times I've had a headache. I do 1 tsp of ACV in 6 oz water at night before bed. I thought it was stress until I saw your post.
Apple Cider Vinegar
I have been trying to take this apple cider vinegar to lose weight mixed with water and cayenne pepper and lemon juice... But when I do I get a headache.....does it have anything to do with my medicine that I take....bp med latansan, nexium and crestor alliegen med?