Drink isotonic sports drinks rather than water. Get your flat mates to pop to the shops and get you some.
They have the salts and sugars in them that you need just now. You probably know that anyway.
Would it be possible to try custard or something like that, rice pudding, tapioca etc. Soft but solid foods.
If thats not working my staple stand by is soup. You can soak bread in it so that you dont have to chew it at all but it makes it more filling and you get more useful things into you.