When backpacking for several days, is there a benefit to drinking coffee and the likes in the morning, or does the crash that comes later in the day hinder the progress of a group in the back-country?
There are various popular beliefs that alcoholic and caffeinated drinks "don't count" for hydration because alcohol and caffeine dehydrate you. In fact, beer consumed in moderation has a hydrating, rather than a dehydrating, effect,[Valtin 2002] and laboratory studies have shown that caffeinated soda is just as hydrating as water, i.e., the diuretic effect of the caffeine is too small to measure.[Grandjean 2000] Even in the case of coffee, which has much higher concentrations of caffeine than soda, studies going back as far as 1928 have shown that the diuretic effect vanishes for people whose bodies have learned to tolerate the caffeine.[Eddy 1928]
Caffeine has various positive mental and physical effects, which are one of the main reasons people consume caffeine. It typically improves athletic performance, which would be a plus while hiking.
Caffeine is addictive. However, the time it takes to lose the addiction is typically very short, typically just a few days. Some people may actually lose a significant portion of their physical dependence and tolerance just between their last cup of coffee of the day and the time when they wake up the next morning.
If you have a heavy caffeine habit and suddenly go cold turkey for a hike, the withdrawal symptoms may be unpleasant on your first day. A lot of people think they have physical problems with altitude at elevations as low as 2500-3000 m, and while I don't have any hard evidence, I've always suspected that a lot of the headaches, etc., are not really the effects of altitude but in fact a combination of sleep deprivation and caffeine withdrawal. If you want to avoid withdrawal symptoms, one possibility is just to taper off your habit in the last couple of days before the trip. This is what I do, and it works well for me.
Depending on how you get your caffeine, obtaining it while backpacking may be time-consuming, because you have to boil water. But this is not necessarily a bad thing. Purely as a social matter, a pitstop for tea is a valued little ceremony, e.g., for many mountain guides in East Africa. The hot water may also be helpful if you're in cold weather, and bringing the water to a boil will also kill any potentially harmful microorganisms, although the presence of such pathogens in backcountry water sources has been vastly exaggerated in the popular consciousness. (And contrary to popular belief, it is not necessary to boil the water for any particular amount of time. All organisms capable of causing disease in humans when ingested are killed long before the boiling point is reached, although bringing the water to a boil is a handy way to verify that you've reached the necessary temperature.) If you don't want the hassle of boiling water, and want to keep getting your caffeine fix, there are various other options such as caffeine pills (No Doz), chocolate-covered coffee beans, and caffeinated energy gels.
Eddy 1928 - Eddy NB, Downs AW. Tolerance and cross-tolerance in the human subject to the diuretic effect of caffeine, theobromine and theophylline. J Pharmacol Exp Ther. 1928;33:167-174.
Grandjean 2000 - Grandjean et al., "The Effect of Caffeinated, Non-Caffeinated, Caloric and Non-Caloric Beverages on Hydration," Journal of the American College of Nutrition, Vol. 19, No. 5, 591-600 (2000) http://www.jacn.org/cgi/content/full/19/5/591
Valtin 2002 - Heinz Valtin, "'Drink at least eight glasses of water a day.' Really? Is there scientific evidence for '8x8'?," Am J Physiol Regul Integr Comp Physiol 283: R993-R1004, 2002. http://ajpregu.physiology.org/cgi/content/full/283/5/R993
I drink caffeine in mass quantities. It's hard to find me not drinking a coffee, Coke, or something similar, here in the regular world.
But when I'm out in the backcountry, I only rarely drink it. I find that I just don't really need or want it.
When I started my hike of the Appalachian Trail I brought a coffee press attachment for my Jetboil and coffee, milk and sugar. The whole nine yards. I even used it for a few days and enjoyed my morning coffee. But it was a lot of hassle, and I sent them home from Neels Gap, mainly to save weight. Though I didn't miss the hassle and I found that I really didn't miss the caffeine either.
I do still drink it when I'm in town or at a hostel or something, but I just don't bother taking it out into the backcountry anymore.
If you normally have a coffee in the morning then you will be fine with a coffee in the morning out on the trail. It is part of your daily routine.
It is useful to have something like red bull or energy drinks in a pack as part of your emergency rations as week. Not for long term but if you need to stretch a few final miles late in the day due to delays it can help.
Well in my personal experience, I've never faced any issue with caffeine while on a trek. As mentioned by Rory, if coffee is a part of your morning ritual, it will not make much of a difference. Too much of caffeine is not good while on treks as it does dehydrate your body. A better substitute would be tea. Usually on higher altitude treks, tea is a beverage used regularly along with garlic soups. Tea also happens to have caffeine but the quantity is much lesser (almost half that of coffee).
But always remember, never overdo. Keep water as your primary source of hydration.
Hope this helps. Cheers!