Coffee. I haven't found an instant that I really "like". I will drink one, as the warmth is good, especially on a cold morning. I also take along individual pack, sugar-free, hot chocolate mix. I can tolerate the instant coffee flavor, either with some of the mix added or with the two combined, better than without. Still, this is more of an "emergency" solution.
If I'm going to drink coffee at all, it is hard to ditch some sort of brewed coffee. I can grind enough from fresh beans ahead of time and carry minimal added "hardware" to deal with the brewing process. So, that is still my preferred answer. A minor "luxury", assuming enough time, water and a heat source to boil the water.