I was wondering about the vinegar, too, and the sugar.
Perhaps try a plain cooked beet, when the throbbing has subsided. See how that sits with you.
Later, you could try a raw beet, maybe with a few of the greens.
(I have a passion for a big feed of beet greens once in a while, usually lightly cooked...with a bit of butter. When I'm feeling very 'purist', I want unsalted butter, because I'm sure they don't use the best salt in butter. Though unsalted butter is always more expensive. Why is that?)
Unheated Apple Cider Vinegar is great over cold cooked beets, with some mixed 'pickling spices', perhaps ground...and a touch of grade C maple syrup. Let it sit for a while...maybe overnight. This might be better for your liver.