Bought too much daikon recently and ended up making two types of quick pickled radish.
Korean style and Vietnamese style. Seems that the main difference was the use of white vinegar in the Korean one and Rice wine vinegar in the Viet one.
Perhaps we used crappy rice vinegar, but the Viet style turned out pretty bad.
The Korean ones were absolutely fantastic and will be doing it over and over again.
For the Korean one.
Equal part water, sugar and vinegar. I used boiled water to disolve the sugar and stir through. Added a bit of salt (didn't measure that part) and poured it over the cubed daikon in a jar.
Left in fridge overnight and it was beautiful.
You can probably mess around with other spices, but that's all I did.
The Viet one was this https://www.recipetineats.com/vietnamese-pickled-carrots-daikon/#recipe