Turn on a multi-functional pressure cooker (such as Instant Pot(R)) and select Saute function. Add bacon and cook until almost crispy, about 8 minutes. Take your time cooking the bacon in order to render out all the fat. Add onions and cook, stirring frequently, until soft and translucent, about 3 minutes. Pour in vinegar and scrape up the brown bits from the bottom of the pot. Pour in beans and their liquid; season with salt and pepper. Stir in radishes. Close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 5 minutes. Allow 10 to 15 minutes for pressure to build. Release pressure carefully using the quick-release method according to manufacturer's instructions, about 5 minutes. Unlock and remove the lid.