My first two days I had headaches like you wouldn't believe, but I am happy to report that it's day 10 of my 30 day fast (never done one before), and I'm not hungry, tired or sick. Be careful with citrus, grapes and pineapple, the acid content can be pretty tough on the tummy. Carrot works fantastic for nausea. Carrot apple is very good, but my favorite is a mix of lemon, carrot, beet, celery, parsely and tomato (a homemade V8). After a while I found the sweet juices to be a little sickening and preferred the less sweet juice.
I also found that good quality herbal teas with a little honey stave off the chills and nausea. Vegetable broths are ok too. I found a good organic vegetable broth to drink. Only problem with that is that it has 0 calories, so it won't help with energy.
Try out your favorite fruits and vegs. You'll find a mix that you like. Don't quit. It's hard. I have a husband and 2 kids I have to cook for too. It's a challenge, but one I hope is worth the effort. Just make sure to use only fresh juiced stuff, no bottled, or canned. You will get the most nutritional value and health benefits from the fresh as compared to the "dead" bottled varieties.