I can't drink on an empty stomach when I'm nauseous, so I'd eat something easy like graham crackers or cereal and then drink water, or juice, or 7up or seltzer. 7up is what I have the easiest time drinking, it settles my stomach. I know soda isn't ideal but it's better than nothing or throwing up. Then there's all the usual nausea cures to try, ginger, B6, pressure points, and there are medications if it gets so bad you really can't eat or drink. For me they do get more frequent when dehydrated but I'm almost always going to get quite a few BH anytime after like 13 weeks.