Used copies for PlayStation 4 or Xbox One are plentiful and cheap ($5–10). Consoles don’t require online activation for disc-based single-player play.
Downloading copyrighted software without permission is piracy. While individual users rarely face lawsuits, ISPs may throttle your connection, and you violate DMCA or similar laws in your country.
You can find FIFA 16 PC DVDs on eBay or Amazon Marketplace. However:
Many “ISO link” sites lead to survey scams, fake torrents with zero seeders, or broken archives. You could spend hours downloading a 15 GB file only to find it’s corrupted or password-protected with a paywall.