Unfortunately, it differs for everybody! Check out the Hyperemesis Support thread on here for various solutions. I am coming out of that phase now, but I found the worst thing was to actually have an empty stomach. Try to eat a little bit every hour or so, even if it's just a couple of crackers.
Make sure you're drinking lots - if water won't stay down, try some peppermint or ginger tea or some Lucozade maybe?
Things that helped me at work were: dry nibbles (crackers, biscuits, plain crisps - though oven baked were best as standard can be a bit greasy which was a big no no!) when it was very bad, a bit of protein when it was more bearable, like little cubes of mild cheese.
Try looking into acupressure bands too, I found them fab for work. Just click the little disc when you're feeling sick & it helps to soothe the nausea. Easy to be discrete with them too! And they're cheap.
If it remains hideous, I'd go and see the doctor. They can give you medication for it and it's much better for you to be healthy & hydrated! Sympathetic hand holding is always available on here too
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