Sorry, I still don`t understand what you mean by soaking the monitors, unless they drink the water they`re put in, soaking in itself won`t rehydrate them?
And how would offering the dog food with added water be very useful, surely it will be a soggy "mush", and a mouse or rat contains lots of fluid, too!

I totally agree, Varanids SHOULD be healthy, alert and active, unfortunately, that doesn`t last too long for most captives...