Eat VERY light! Bland foods only (rice, white crackers and such) and only in small amounts! Heavy or spicy foods can cause the body to violently react and you'll puke it all back up again.<br />
Do not drink "tons"of water. Drink room temperature water bit only in sips! You can drink as much as you think you want, but no more (you'll just make yourself sick).<br />
Once you're over the flu, drink away as you'l be very dehydrated. Don't go for heavy foods right away, give it 48-72 hours before going back to those.<br />
Your stomach will thank you.
Drink gallons of water.