That sounds like an awesome trip!
If the DNR does not specify what type of container or bag is needed, then your friends should be able to use a regular, waterproof stuff sack. I love that you are already educating them as to wildlife protection! Please make sure they know how to hang a bear bag correctly before y'all go; YouTube has a handful of good videos if you search "How to hang bear bag PCT method."
A lot of the times, though, I will carry my bear can even if it's not required by the local agencies because it doubles as a camp stool, it's a super easy/quick system that you don't have to worry about, and it protects my food from mice. While I've been lucky enough that it hasn't happened to me, I've seen mice chew through other hikers' food bags that were hanging on the cables. Nothing like sharing your Pop Tarts with the field mice!
I hope y'all have a great trip! Update the community with photos and/or a trip report once you're back!