Methamphetamine was largely used by both sides, but it was most prevalent in the German and Japanese armies. The drug was distributed in large quantities to all elements of the German army, from foot-soldiers to elite troops and pilots. Between April and July 1940, Germany produced more than 35 million three-milligram doses of Pervitin (the German trademark for meth). Japan is estimated to have produced one billion Philopon (their trademark) pills between 1939 and 1945.

Meth is cheaper to synthesise than amphetamines, particularly in industrial quantities. It would have been difficult for soldiers to have been provided with cocaine in the same quantities as they were with methamphetamine, as the coca plant can only be grown in South America. The Germans did create an experimental cocktail called D-IX containing 5 mg of cocaine, 5 mg of oxycodone and 3 mg of Pervitin in each tablet. D-IX allowed Prisoners at Sachsenhausen to march 55 miles while wearing 20kg (44lb) packs. It was planned for all German troops to be supplied with D-IX pills, but the war ended before they could be mass produced.

Meth possesses both stimulant and performance-enhancing effects. Meth was provided to soldiers to lessen the toll of the mental and physical exhaustion and maintain focus. It allowed soldiers to stay awake and gave them a sense of euphoria, which was a benefit to moral.

Amphetamines were also largely used in the Second World War, often in a similar way to methamphetamine. Allied bomber pilots were provided with it to aid their focus and reduce fatigue on long missions. They could also be found in US first aid kits, for exhausted soliders.

EDIT I: More detail on cocaine/D-IX

EDIT II: u/t-o-k-u-m-e-i's correction

Followup, what were the effects of this on soldiers after the war? Were there many that became addicted?

In French fighterpilot Pierre Closterman's WWII autobiography, he tells the story of how his doc doubled his dose of both amphetamines and downers as Clostermans nerves became increasingly frayed.

The implication being that amphetamines were routinely distributed to RAF pilots during the war.

As an aside, there has recently been debate over the wisdom of the US air force mandating the use of amphetamines on long missions for their pilots.

Some doctors worried about a correlation between attacking friendly forces by mistake, (blue on blue) and the use of amphetamines by US pilots during the Iraq wars.

My point being that this practice is by no means stopped even today.

I'll copy and paste one of my old answers that pertains specifically to Germany:

In 1938, the Temmler pharmaceutical company based in Berlin released a drug called Pervitin to the civilian population of Germany. Pervitin is another name for methamphetamine (in fact, in large parts of Eastern Europe, methamphetamine is still commonly referred to as Pervitin when in pill form).

Otto Ranke, head of the Military Medical Academy at the University of Berlin and member of the National Socialist Teacher's Association, tested the drug's performance enhancing abilities on university (volunteer) students, recommending it for use by the military. Even before this, Pervitin was being issued by medical officers without military order or procedure, especially in Poland and the occupation of Czechoslovakia. Ranke writes in 1940:

"According to the personal information of some officers, Pervitin was repeatedly used during the Poland campaign, even supplied by army physicians.

Dr. Grosselkeppler of the 30th infantry division writes:

"As the drug [Pervitin] was known to the medical officer due to its positive effects, it was bought before the Poland campaign. (...) The pills were distributed without comment. Owing to their remarkable effect, the troops came to know very soon what their purpose was."

Use was widely reported among Luftwaffe pilots (the tradition of giving pilots pharmaceuticals to stay awake is still around today). 36 million pills were sent to German soldiers in France alone.

Many field doctors noted some signs of addiction among soldiers issued Pervitin- longer recovery times, reduced effects, cardiac/respiratory problems. Ranke studied cases of usage of Pervitin in Poland and France during 1940 following reports of abuse by officers and medical officials, but there's evidence to believe that he purposely lied about his findings in order to diminish the problem in the eyes of the administration. In 1941 an amendment to the Opium Law of 1921 medicalized Pervitin for German citizens (possession was illegal without a prescription), but military use continued, with an additional warning about addiction issued to commanding officers handing out the pills to soldiers. I couldn't find any sources that cited examples of soldiers disobeying orders or creating unruly disruptions specifically due to Pervitin. In fact, quite the opposite- I quote an English translation of a letter from a field medic in 1942, during a retreat from the Red Army in freezing weather:

"In a 14-hour march without contact with the enemy, 25 km were covered in partially deep snow. (...) the snow sometimes being hip-deep, the nervousness (i.e. emotional agitation) of the men resulted in a pace that was too irregular and too rapid. When the ice of Lake Ilmen was reached, (...) many comrades showed signs of total exhaustion: staggering, a complete less of interest and willpower, pain and cramps in the leg muscles, the calves and groin especially, palpitation, pain in the chest, and nausea. Around midnight (6 hours after the retreat had started) some of the troops repeatedly tried to lie down in the snow, their willpower could not be aroused despite vehement encouragement. These men were given 2 pills of Pervitin each. After half an hour the first men confirmed their improved state of health. They were marching properly again, stayed in line, were more confident and took notices of their surroundings. The pain in the muscles was borne more easily. Some proved to be in a slightly euphoric mood. With only 180 pills at hand, the medicine could only be distributed to the seriously exhaused."

However, there are numerous documented examples of soldiers becoming addicted to Pervitin, most notably in the case of Heinrich Boell, who wrote several letters to his family from military training:

9th November, 1939: "Dear parents, brothers and sisters! [...] My duty is very strict, and you must understand when I write only every two or four days. Today I am mainly writing for Pervitin!" And as a P.S.: "Don't forget Pervitin [...] God punish England!"

20 May, 1940: "Perhaps you could provide me with some Pervitin for my supply?"

19 July, 1940, stationed in Poland: "I am tired to death and will now finish [this letter]. Send me, if possible, some Pervitin soon and [...] cigarettes; also a pair of underpants."

Some concerns about officer abuse during the campaign in France lead to an investigation. Ranke collected reports on personal usage of Pervitin from medical officers during his stay in France; of 20 asked, only 5 had not used Pervitin (humorously, at least to me, 8 of those asked had used Pervitin in order to drink more or stay longer at evening parties, or as a 'hangover cure'). At least two officers died of myocardial infarcations after ingesting Pervitin, and one tank commander suffered a heart attack after only taking one pill.

Source: Eckart, Wolfgang Uwe. Man, Medicine, and the State: The Human Body as an Object of Government. Franz Steiner Verlag, 2006, pg. 61-78. Print.