Beet relish was an unintended add-on to my St. Patrick's Day corned beef. When I had my DIY Cleanse and juiced, I made sure to use the discards from every fruit and vegetable.
In the case of beet remains, I added a boiling mix of cider vinegar, sugar, salt, dill,and horseradish in a clean swing-top jar. It sat in the fridge for about a week and what the heck, here we are. The interesting difference between this and other beet concoctions is that mine started raw. A bite was much more earthy and my insides were dyed a very striking pink hue (beware when you pee).