I've done the same job in 3 very different sectors, and while there's still quite a bit of me thinking, "I have no real understanding of what we do," that's not actually entirely true after a certain amount of time (years...) There's a lot of stuff I don't know, but I do know where to look it up.
The most important thing is they think you can do it. The skills you have are actually mostly to do with communicating to people, and you may need to learn some stuff about construction products rather than food products, but you'll still be using most of the same skills.
Secondly, even if you knew the sector inside out, you'd still have a ton of stuff to learn - IME, the thing that makes new jobs most difficult is learning the different ways of how to contact the IT helpdesk, how to apply for password resets and new accounts, how to record time and expenses, which forms to fill in - that sort of thing is different for pretty much every company, and people know it takes a bit of time to start getting the hang of it. If there's some sort of introduction to the company course, take part, and ask the questions about the things you want to know.
Ask if there's an acronym dictionary or something - my company has an online one. It's not perfect, but it does include most of the major internal jargon, and you can ask for new terms to be inserted which they will then ignore. We also have databases on our customers and our products, so look out for something like that.
If you're in meetings and don't know something, then ask them to explain - chances are you won't be the only one, and at least you've got the excuse of being new!
You will have a learning curve, but you can do it! Also, 5 minutes vs 45 minutes commute will make a massive difference to how tired you get - a new job always is tiring, but less travel time really does help.
Good luck!