I'm new to dehydrating but my limited experience is that if I put my evening meal in a Nalgene 300ml bottle after breakfast and put water in to cover and maybe a fraction more, that is sufficient to rehydrate by the end of the day ready for heating up to eat. A little more can always be added when heating but it's not so easy to take some out. What I've also found is that the meat content needs to be either minced or cut up really small, otherwise it takes too long on the stove and is wasteful of fuel. Chilli Con Carne with minced beef was perfect but a chicken and bean stew was not so good as the chicken pieces hadn't rehydrated enough.
Backpacking round the UK