There are various methods that people might consider when they want to convert their Google Play cards to cash. However, it's important to note that not all of these methods are legitimate or legal.

Some individuals might attempt to find online platforms or services that claim to offer this conversion. But often, these can be scams. They may take your Google Play card details and then disappear without providing the promised cash. It's crucial to be extremely cautious when dealing with such offers.
Legally, Google Play cards are intended for use within the Google Play ecosystem to purchase apps, games, movies, and other digital content. Trying to convert them to cash through unauthorized means goes against the terms and conditions. It's advisable to use the cards as intended for a legitimate digital purchase rather than seeking illegal ways to turn them into cash. This helps ensure a safe and proper experience within the digital marketplace and avoids potential financial losses and legal issues.