The best way to find new Fit Piece 2 codes is to keep an eye on the official Roblox Fit Piece 2 page. The developers often post new codes there, as well as news and updates about the game.

Launch Fitness Simulator 2 on Roblox. Tap the Codes tab on the right, next to the Daily tab. Type or paste an active code in the "Enter code here" text box.