Although this is obviously an important time for fetal development, think how TINY the baby is- it really needs very little else other than to be protected from harmful stuff, which is probably the reason 1st trimester nausea/ vomiting exists in the first place. Most of the the really junky food out there- all that processed, white fluffy stuff that can be kept down (crackers, cereal, white bread, etc) is fortified, so you are getting something. And think of the average fast-food consuming American out there- I would bet that a solid chunk of the US eats even crappier than you right now, just probably much higher quantities, and not to say that they are healthy but you sure can survive a long time on nutritonally devoid food. Carnation Instant Breakfast tasted OK to me some days, and is less thick and medicinal that Ensure etc. If stuff is relatively thin or liquidy, and you eat in small (like 2 bites at a time) quantities it will probably be more likely to stay down long enough to digest some before you throw it up.
So, no need to worry about your baby but this sounds awful for you. If something works, eat it even if that means 3 meals per day. And if nothing works, and you have hyperemisis or get dehydrated or something, and you can't take anti-nausea meds, there is always the option of IV fluids and nutrition. So if you are really worried, and nothing is staying down at all, let your provider know and if they are worried about your intake they will do something about it. But if you can keep down crappy cereal and drink a few cokes you will survive and your baby will be fine.
This is my first pregnancy, and the nausea/ vomiting was as bad as I ever imagined it could be (short of having hyperemisis) and I am finally getting a bit better at 14 weeks now. But I spent about 6 weeks being able to eat little more than cereal and Yoplait yogurt and McDonalds and Coke. Anything nutritional I threw up so I just stopped trying. I am SO thankful to be off the McDonald's now and have been able to eat vegetables for a week. Woohoo!