I 100% feel where you're coming from, and - not in any boastful manner - I believe I've perfected this situation.
When I cannot eat for whatever reason, be it between MDMA/sleeping, in withdrawals, in depression, etc, it always seemed to cause the same appetite-erasing effect. Here's what I did / what to keep in mind. This does not need to be copied, as it applies to many combinations. There is no "healthiest"/"best".
Simply put, fluids + weightgainer + multivitamin. Remember, water is as - more, even - important than food. Make sure you're hydrated, dehydration kicks in faster than hunger / can be more of a problem here, and hydration is ESSENTIAL to the next step (food/calories/nutrients). Without hydration, any food/nutrient will be a problem.
Once water/fluid is controlled for, calorie/nutrient density, as far as you can stomach it, is key. Remember to look for not only heavy vitamins/minerals*, but for the 3 macronutrients (fats, proteins, and carbohydrates). Remember that carbs will boost blood sugar, which can be useful, but that carbs are NOT needed. The body can make carbs from proteins/fats via carbonucleogenesis (sp?), but it cannot make proteins(amino-acids) or fatty-acids, they must be ingested.
(*if I were referring to a post-mdma/before bed meal, I'd say go crazy with vitamins/minerals, however, if we're talking about someone who's, say, in methadone withdrawals (long!), then I'd advise caution with fat-soluble stuff. For instance, vitamin C and the B's are water-soluble, the excess is urinated out. Vitamin E, Iron, etc are not - this can cause an issue if taken long-term in excess.)
Once you have fluids, macronutrients(fat/protein and, typically, carbs), and micronutrients (vitamins and minerals) covered, fiber ends up being a good consideration. Fiber is either soluble or non-soluble, both help but soluble fibers are good because they give bulk to an otherwise empty stomach.
For example, personally, I would make a weightgainer shake. The density would depend solely on my fluid levels, I'd make it more watered-down the more water I needed. I would consume it with a proper amount of a multi-vitamin/mineral supplement. I'd consume fiber, typically psyllium husk, either as a powder mixed into my shake, or as capsules swallowed with my shake. The weightgainer I used would be modified to a proper meal - for example, if it were a carb-heavy weightgainer (as most are), I'd use milk to mix it (for protein), and add olive oil (for fat). I'd always consume fish-oil capsules along with the vitamins/minerals, and fiber.
Given where I worked, I had an extensive selection of protein/weight gain powders on hand, but that's not needed. You could simply use milk + cream(or olive oil), that'd give you solid fluid+fat/carbs/protein, and adding a strong multi-vitamin/mineral is important. Adding the fish oil is a huge plus, and the fiber is more of a comfort thing than a nutritional thing.
I should clarify that this is suitable to keep your body running (quite) solid in these times. It covers what the body needs to intake to function properly w/o malnourishment, and should be very comprehensive. Over a long period, over life, of course this is unhealthy - you need to eat a variety of foods for all kinds of things that make a difference long-term (antioxidants/enzymes/etc etc). But for after rolling, or a few weeks of withdrawal, this will stock your body with what it needs, despite being fast/easy to get down. The more real foods you can get down, the better, but this formula works* very well in short-term situations where nutritional issues like this arise ;-P
(*provided that the multi vitamin/mineral is sufficient - for one-time, post-MDMA use it's a simple situation, go with strength here. For trying to stay healthy during a month of withdrawals, vitamins - if you're relying on supplements "a multivitamin/mineral" - become more of a concern to balance. Feel free to ask more on that or about vitamins/minerals relative to specific drug hangovers/withdrawals. I'm not too knowledgable on all of them, but others here are (and there's plenty of references here on the boards as to what to use after <insert drug here> or during <drug's> withdrawals). Cheers
