Did you try Jello? When our guys had rotavirus, they both ended up in the hospital, on IVs, etc... The nurses always counted the volume of Jello consumed as part of their fluid intake, rather than as a solid. They make both sweetened and sugar-free varieties. Works for grownups, too. We've always got several boxes in different flavors on hand for yucky tummies. Good luck.
As for the lack of sleep, the only thing that worked for me was following the 'when they sleep, you sleep' rule.