ask for better drugs, thats what i did when they gave me t3s for my wisdom teeth and i got percs...
haha but seriously, if you cant do solid food why dont you eat something a bit better than a slim fast. Make a smoothie with berries and banana or whatever you like with some whey protien, some coconut milk or oil, maybe some cream or yogurt and anything else youd like. Still not as good as a real meal, but it should fill you up pretty well.