Container Backpack

Are backpacks allowed in Universal Theme Parks?

I’m going to The Wizarding World of Harry Potter next Saturday, and I wanted to bring a backpack. I’m going to fill it with empty plastic water bottles, so I can fill them with butterbeer, as they don’t sell sealed butterbeer containers. But would they allow me to bring a backpack in?
Please offer references or explain, if it happened to you.
So if it’s on the website, link to it! I searched the site and couldn’t find it. Use the damn references section, please!

It’s on the website about what you can and can’t bring. Yes you can bring the backpacck but they will search it. On certain rides you’ll have to take it off and put it in the lockers.

Nutnfancy Backpack Loadout List: Moonscape Adventure