I'm anopther HG survivor, I also used to work on a support line for Mums with HG (the charity folded but the website blooming awful is easy to find if you search that, and has fab tips)
personally and from the women I spoke to on the line, I wuld skip bread, anything heavy , and fried foods. But it REALLY depends on the individual. The best foods for severe sickness are:
A) anything you can tolerate
B) Anything that tastes OK coming back (well realism LOL)- ornages and chocolate cake
C) anything with a high fluid content,a s many people struggle with fluids. Lettuce, melon, cucumber, ice pops, plain ice, are all good.
The thinkg is not to focus on getting a basic nutritional intake- you can't so that's theat. Its to focus on keeping yoursel;f off a drip, and therefore hydrated. The baby won't suffer, your body will feed the baby before you.
As for the sleep- proven link between exhaustion and sickness / nausea iirc
Oh and if you get the excessive salivation sucking a lemnon slice can help some people