No, not that kind of trick.

Have you heard about it? Supposedly, when you check in to a Vega$ hotel

• you present your credit card wrapped in a twenty;
• you then ask if there are upgrades available;
• if there are, you get the upgrade and the clerk will keep the twenty;
• if not, you get your twenty back.

Apparently, it also works for car rental upgrades.

If you try it, and it works, let me know in the comments.

Here’s the site.

There’s a FAQ too.