If you buy a UPS label, you don't need to use special UPS-branded boxes or envelopes. You can use either your own custom-branded packaging, or generic boxes and envelopes (think regular brown or white packaging).
That said, if you choose to order free Express packaging from UPS, you'll need to make sure you're buying an air-based UPS service, like 3 Day Select®, 2nd Day Air®, or Next Day Air®. That means you can use Express packaging for every domestic UPS service except Ground 😅
How do I order free Express packaging from UPS?
If you want to order free Express packaging, you'll need to create a free account on UPS.com. Once you make your account and order your boxes or envelopes, UPS will deliver your packaging to the address you provided when you signed up 👍
Learn more about free packaging for UPS shipments.