In the US today it is very easy to find ways to 'rev' your engine, so to say. The prevalence of coffee purveyors is at an all-time high and tea is getting raves, especially green tea, as a source of antioxidants. The counters which we can buy drugs over are often almost blocked by the piles of 'legal speed' that are being offered for sale.
These 'uppers' consist largely of caffeine and/or pseudephedrine for the active ingredient(s) and various herbal and manmade stimulants, along with vitamins, minerals, amino acids and loads of sugar and flavorings(in the energy drink category). The herbs guarana and ma huang are common sources of caffeine and ephedrine respectively. The ban on ephedrine is often ineffective; importers get much through the borders. Products containing ephedrine are still showing up. Synerphine from bitter orange has a similar effect and is legal. These stimulant drinks and tablets often contain the vitamins and amino acids and minerals that are found in any full spectrum 'vitamin pill', at a greater cost than necessary. The desired effects of wakefulness and weight loss(if this occurs at all) comes with a cost. The side effects have been fatal. The heart is stimulated along with the nervous system, increasing the pulse rate and blood pressure. The kidneys get overworked which is not good. Anxiety, nervousness, insomnia, sweating and dizziness are all problems when using this stuff. The drinks that add vitamins, herbs, amino acids and other ingredients rarely contribute to dangerous levels of these unless one imbibes too freely. Theobromine and theophylline are found in chocolate and tea; they are related to caffeine and are often beneficial in very small doses, for instnace they can help asthmatics breathe easier. Dogs are poor at metabolizing theobromine from chocolate which is why they can die from ingesting candies made of that. Cats can also but they usually won't eat it. Theobromine has a side effect of relaxing smooth muscles, which is good sometimes but bad other times. All your sphincters are smooth muscle controlled. The pharynx relaxation can cause reflux; in other words your gullet can relax, which means your stomach contents may be burped up and burn your esophagus. The bowels and bladder will relax too, which may cause trouble.
Then there is something called "rebound hypersomnolence". This is the "crash" that you get after a few hours on these uppers. The body that you have pepped up with artificial stimulation is tired, and the chemicals are used up and the reaction is to be more tired and sleepy than before. To ingest more can work for an hour or two or three but the cycle will just be delayed. The best way to handle these problems is to plan your day better and exercise youur muscles and your thinking; don't fall for short term fixes that only postpone things. Better planning can help you avoid cramming the night before a test or trying to lose weight without watching your diet; and exercising regularly will reduce your weight and help generate the feelings of well-being that preclude anxiety and stress in the first place.
On the other hand, the need to sleep when you are TOO nervous, or anxious, is NOT very widely addressed by the OTC(over-the-counter) drug industry. The few drugs available without a prescription tend to be antihistamines such as chlorpheniramine maleate or diphenhydramine. These will make one drowsy but they are not very effective except if you want to crash the car. The benzodiazepine(Valium+ Xanax) family of drugs is very effective but they require a prescription because it is easy to get habituated, and much abuse occurs. The similar acting barbiturates are even more dangerous. Rarely seen today, the 'cold-turkey' withdrawal from these is often fatal. Even moderate use can involve bizarre and dangerous memory loss, social disruption, violence and intoxication. Stay away from this family of drugs, though a proprietary mix of belladonna and phenobarbitol can ease chronic gastritis. Poppy tea can work as a mild sleep-inducing drink but the federal agents that beat your door down may wake you up, plus you will get little sleep trying to buy ever more from dangerous sellers in dark alleys.
Methaqualone hasn't been sold for years; newer preparations, all prescription, have had mixed results. Some swear by them. I am unwilling to experiment with my liver until more time passes.
So what is there that is natural, effective and safe? The best two things around for me have been a root,valerian, and the natural body chemical, melatonin. Valerian is an evil smelling, though not too hideous tasting powdered root from a plant that is grown worldwide, it originally comes from Europe and Asia. The Wikipedia article tells much, including that it smells like a wet dog! This is a great analogy, unfortunately. There are two warnings about possible night terrors and a mutagen(cancer-inducer) that may be in it. I have had good luck with the stuff myself but haven't used it overmuch. The other chemical, melatonin, is from the brain itself, and is available in dollar stores. It works in a mild but effective manner. As it naturally occurs in the body it is far less harmful than anything you can find elsewhere. It will not knock you out but if a slight tenseness is keeping you awake, it will help . It turns into tryptophan, an amino acid in turkey that is known to help one sleep.
I have been writing these words from experience, backed up by reading other sources, mainly Wikipedia, where I just learned some very interesting things about melatonin. It is a hormone, which usually can be seriously dangerous to mess around with. This chemical is rather safe, and it is an antioxidant, and has other interesting properties. It was first discovered when researching color change in reptiles! A patient in one study got relief/sleep from 1/2 a milligram but not from 20 milligrams, so try a small dose first. They are sold in tablets, OTC in Canada and the US but not in Germany. As with any advice here or elsewhere, read the labels, inserts and online. No blogger can write the amount of information you can find with even cursory investigation. We can but give mere hints and clues to what you need to know, especially for your individual needs. The column on potassium is an example. I just read that Lisinopril (a very good hypertension med) takers can experience drastic increases in potassium levels and must watch for that. For an ironic factor, this drug and other ACE inhibitors were discovered and developed from a pit viper venom!