What are the least harmful ways to maintain performance at night can you advise not to ditch the heart?

If you avoid the chemical method, then as a physical method, deep breathing with a full chest is suitable as indicated above, you need to breathe for several minutes. In general, if you know that you are more productive at night, then start rebuilding your sleep schedule in advance, so that by the time of your greatest productivity, you will be awake. It is also good to adjust the work to the daily biorhythm. But I am already deviating from the main topic. So even to the physical method, you can add exercise during work, and the muscles and joints are high, and even gives the body a general tone. By the way, no one canceled motivational videos or music (especially for productivity Mozart is good), his compositions are not too emotional and not too boring.

The question is, why do you need this kind of work at night? If you, like 95% of students, decide to learn all the tickets on the last day before the exam, this is a bad idea, if only because no matter how hard you suffer, all the knowledge that has been trivially crammed into your head will not be learned. The process of memorization takes place in our sleep. For students actively preparing for a session or writing a term / diploma / dissertation work, I would recommend a term intake of nootropics at least two to three weeks before the "X" hour (the effect is cumulative and does not develop immediately)

If your desire is not sleeping at night is not associated with intellectual work, then caffeine and taurine (the main components of energy drinks) are quite capable of coping with the task, but taking energy drinks regularly is very harmful. On the other hand, there are longitudinal studies showing that in fact, regular coffee consumption does not increase the risk of developing cardiovascular diseases, and high blood pressure and tachycardia are usually observed in those who drink coffee rarely, but a lot. This is by the way about your mark about the heart, apparently referring to the very myth about the dangers of coffee.

Also, for completeness of the answer, mention should be made of the pharmacological group of analeptics. These drugs are used in the treatment of sleep disorders such as hypersomnia and narcolepsy. The most common among them are amphetamine derivatives. As you can imagine, these drugs have narcogenic potential and are prohibited for use in the Russian Federation. So I cannot recommend them at least for formal reasons. However, from a medical point of view, amphetamines have a number of limitations, and even regardless of their legal status, they cannot be recommended in this request.
A relatively modern means can be considered a new generation analeptic - modafinil. It is devoid of the disadvantages of amphetamine, and yet, unfortunately, it is banned in Russia even for medical use. So I am writing about it purely for educational purposes.

Summarizing the above, you should clearly understand that any psychostimulant cannot be considered completely safe (even banal caffeine in large quantities) so maybe you really should look for options not in pharmacology, but in physiology. For example, try to practice meditation and yoga nidra, which in turn can reduce the need for sleep.

ps
I will comment on the answer about oxygen and breathing. The tip says to take 5-10 deep breaths. So that's it. Never force breathing. You need to breathe correctly. With hyperventilation, you first get hypocapnia (carbon dioxide is washed out of the body), as a result of which the vessels narrow, which leads to hypoxia (lack of oxygen). And it doesn't matter how much fresh air you breathe in, because oxygen with this breathing regime simply will not reach the cells. You need to breathe smoothly, measuredly, calmly. Long breaths in and out. This breathing is useful for panicattacks, but whether it will help you stay awake at night is a big question.

You take a couple of liters of water and just drink while you study or do something important. Your bladder activity is unlikely to keep you awake.

Oxygen is the best and most harmless means of making work rich and productive. Someone has an oxygen cylinder at home for cases of long and strenuous work, someone in the old fashioned way opens a window and takes 5-10 deep breaths. When oxygen enters the brain, it enables the brain to function.

If one-time, coffee and energy drinks are possible, do not plant your heart at once. If you need to support yourself every night, change your daily routine and get used to working at night, don't even think about any coffee or energy drinks!

The easiest way is to buy caffeine in a pharmacy, it costs a penny and there will be more sense from it than from energy drinks, which, in addition to caffeine itself, contain a bunch of things that do not have a very negative effect on the body. Personally, I was once helped by an espresso, poured into a two-liter bottle of cola - I stayed on my feet all night, and in the morning I was quite cheerful, though my heart ached a little. As for me, caffeine is a little annoying, it's hard for me to focus on it personally, it is better, in the absence of contraindications, to try piracetam or phenotropil (the second has a better effect and fewer side effects, but, accordingly, the cost is higher), quite safe and effective, just ideal for work or study because they stimulate the brain in the right direction, let's say.