If one is going to do that, I'd strongly recommend putting them in some kind of basin that can hold the water if it escapes from the jugs, or sturdier containers, or both.
At least in the US, water jugs are generally very flimsy. An attic is likely to have wide temperature variations throughout the year, and leaky water jugs up there could cause some expensive damage.
Yeah we had plastic jugs in our cool basement leak all over the concrete floor — I can’t imagine the disaster that would be to have plastic jugs in my 140F attic with resultant leaking down from the ceiling
At least in the US, water jugs are generally very flimsy. An attic is likely to have wide temperature variations throughout the year, and leaky water jugs up there could cause some expensive damage.