Whisk vinegar, water, and salt in a large bowl. Add peanuts and stir to coat. Transfer mixture to a gallon-sized plastic zip-top bag and let sit for 8 hours or overnight.
Pour bag of peanuts and liquid into a multi-functional pressure cooker (such as Instant Pot®). Close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 120 minutes. Allow 10 to 15 minutes for pressure to build.
Release pressure using the natural-release method according to manufacturer's instructions, about 20 minutes. Unlock and remove the lid.