Yeah you just have to sip slowly and very very frequently. Sucking ice is good. Try a little weak tepid tea (no milk). Suck on a bit of lemon/orange etc. Have a bit of jelly and let it slowly dissolve in your mouth. Bit of melon - esp watermelon - to suck on. (You aren't trying to get the food down with the fruit, only the liquid in them.)
The key thing is to not get dehydrated. So each time you go to the loo, vomit or have a heavy sweating session (if you have a temp or are still being active), ensure you have a few more sips.
The Gastrolyte drinks and popsicles are good to keep your electrolytes up and will help keep you dehydrated.
If you can have a mouthful of soup or even a stock cube dissolved in warm water, it will help keep your strength up too.
Personnally, I find water can be too hard on the stomach in these situations, and prefer some stale lemonade (like Sprite) or the weak tea or the fruit/jelly.
And if you get a craving for something to eat, follow it (even if it something that you would normally avoid) but just don't have much of it. Just peck at it. Sometimes when I am sick, I crave fat - the purer the fat the better - so I get tomato sauce sandwiches made with lots of butter or KFC and just eat the skin. I know it doesn't sound good (on so many fronts) but it keeps that sick feeling at bay at those times. (All to do with my kidney failure too I might add!) Point is, your body knows what it needs, so listen to it.