You are asking about DOT (Department of Transportation) per diem, which has different eligibility applied to IRS per diem. It still matters if they are W2 employees (don't qualify), and it matters if they are Long Haul (overnight) and when/if out of the country (crossing into Canada, for instance).

I like articles that are written to the consumer point of view, such as:

https://turbotax.intuit.com/tax-tips/self-employment-taxes/what-you-need-to-know-about-truck-driver-...

"You can also deduct expenses for showering or doing laundry while traveling for business. Keep track of these expenses, as they can really add up."

https://truckstop.com/blog/truck-driver-tax-deductions/

"Sleeper berth expenses

In addition to claiming any hotel nights you pay for while on the road, you can also claim the expenses associated with setting up your sleeper berth. Items that fall into this category include a mini-fridge, coffee maker, curtains, bedding, food storage containers, and even first aid supplies."

Lodging is Actuals; not per diem.