Use a lot of fresh spices. Garlic presses are cheap and you wouldn't believe the amount of flavor fresh garlic can add to so many things. Pasta and rice are great side dishes. I hate fluid restrictions, especially in the summer time. Trying to limit a child to 20 ounces of fluid a day can be rough.
Kids are also very creative when they get thirsty.
These go pretty far on a fluid restricted diet. You can also make your own by pouring juice into a paper cup, cover with plastic wrap and insert a popsicle stick through the wrap before sticking it in the freezer. You can also do this with an ice cube tray and toothpicks depending on the fluid restriction level. Hard candy and lollipops. Having something to suck on and keep the mouth moist can make a huge difference.