I second the water recommendation, and when I'm low on sleep, I also love having a big old cup of coffee and a smoothie for breakfast. I can't always stomach a lot of fruits and veg if I'm extra tired, but a smoothie with almond or soymilk, banana, and spinach really makes me feel better. If you're out and need to pick something up, some of the Odwalla-type bottled smoothies are pretty good. They have a little more sugar than I'd probably choose otherwise, but they definitely give me more energy (and less crash) than a million cups of coffee and waffles or something (which is usually what I'd want). I also like Kombucha, particularly the Synergy Trilogy one. The ginger in it perks me up.

TMI alert: The fiber also helps, because sometimes a good visit to the bathroom is almost as good as a nap.

I drink A LOT of water all day on the days where I've had little sleep the night before. Sometimes with lemon slices added to it. Other things that help on those low-energy days: nuts, Greek yogurt, apple slices, hard-boiled eggs, baby carrots with hummus, dark chocolate -- and as a treat a big iced coffee.

I like 4% cottage cheese at home or the yogurt/banana/honey cup from Pret a Manger.

Also having something crunchy to eat all day at my desk helps - like carrots and red pepper strips.

If I've not slept, I need caffeine and sugar. Not the healthiest, but it gets me through the day.

I would start with some protein though, eggs add cheese and veggies if you like, for breakfast. Then I'd move onto the chocolate and caffeine.

Kombucha.

Coffee

i feel like what I eat really can impact how I feel. In general I feel better and have more energy if I avoid having a large lunch, focus on protein, etc.
However, on days that I have been up much of the night with kids, I often feel nauseuos from lack of sleep. Carbs (ie bagels, etc) are appealing to me, but I don't know that they are actually giving me what I need. What are the 'right' foods for making up a lack of sleep?