The 400 calorie day sounds like me before I started calorie counting, to make sure I at least eat a minimum of 1500 calories. I just don't notice when I should eat, and then food is hard to put together so I put it off.
Drink, on the other hand, I'm good at. I'm up to maybe 3 liters a day because salty water helps my circulation and makes me feel good.
Your story about overeating sweets and feeling like crap and not putting it together... that reminds me of taking a daily multivitamin with my lunch, then consistently feeling so very sick to my stomach an hour later. Took me maybe 2 weeks to figure out the pill was the problem. (I went back to Flintstones with iron, no problem. I'm hesitant to try an adult multivitamin again because I had such a bad reaction before. Plus, I like chewable pills.)