It's extremely important that you stay hydrated, especially if you're getting sick frequently. If you let yourself become dehydrated, you will feel even more nauseated. Sip fluids throughout the day, using a straw if it helps. Try to refrain from drinking 30 minutes before or after eating, however.
You should try to drink about 6 to 8 glasses of water each day. However, if you've been getting sick a lot, you can try replacing some of the water with a sports drink containing glucose, salt, or potassium to help restore lost electrolytes. Alternatively, you can try drinking cold, carbonated beverages, as some women find these easier on the stomach. Other women also find sour drinks, like lemonade, easier to keep down. Avoid drinking too many fluids, though. Liquids can give you a false sense of fullness which may cause you to feel less hungry throughout the day.