It should be remembered that Germany only moved to a full war economy in February 1943. Before this, factories often closed at night, and the Nazi leadership sought to reduce the impact of the war on ordinary people. Hitler even cut some arms manufacturing in 1942 as the e4nd of the war was obviously near.

The 1943 call up represented a desperate time for Germany, and the armed forces were expanded by sourcing ethnic Germans, Nazi-sympathising non-Germans, and by combing out the population and recruiting men previously exempt because of their industrial or other skills. Germany's new territories yielded many recruits.

Many of the new SS divisions were ethnic, such as the Walloon, Latvian, various Cossack, and Croatian units. On top of this, the original SS divisions were leavened with ethic Germans: for example the Das Reich division in Normandy was very largely recruited from Alsatians. Of course younger men were recruited as well.

On top of this, German divisions became smaller. Panzer divisions now usually had two under-strength panzer battalions, and integral units such as the reconnaissance and anti-tank battalions were shrunk or under-manned. Training units were sent to the front and training itself drastically curtained in specialist areas (basic infantry training remained much the same).

This combing out put great pressure on German industry, which now moved to a slave labour model (the choice of the armed forces or recruitment for forced labour was a common inducement for non-German troops). Races previously exterminated were now worked, and massive populations of Ukrainians and such moved to German industrial zones.

A good source is Adam Tooze, The Wages of Destruction.

Foreigners. For instance, at the end, the last SS troops defending the bunker were from the Charlemagne Division.

Those were Frenchmen defending Hitler at the end.

The SS was to a degree the red headed step child of the German armed forces due to being a political private army of the Nazi party and to a degree the praetorian guard of the Nazis. So to expand after maxing out on volunteers they adopted a huge number of non-Germans to their ranks, experimenting with Indian, Muslim, Slavic, etc. recruits. They even pioneered conscripting ethnic Germans in Axis allied countries and occupied territories (7th SS Division Prinz Eugen was made up of Volksdeutsche from occupied Yugoslavia). By 1944 they were getting conscripts via the same replacement system as the rest of the Wehrmacht, perhaps even earlier, I'm not sure. Gunter Grass, the German author, was conscripted in 1944 and sent to the Waffen-SS. The Wikipedia article is actually pretty good describing the various expansions of the Waffen-SS from the pre-war through the end. There were various major expansions from 1940 on, though AFAIK the 1942 period saw the mass use of foreign troops to expand.

https://en.wikipedia.org/wiki/Waffen-SS

Hitler authorized the formation of units composed largely or solely of foreign volunteers and conscripts. Foreign SS units were made up from recruits in Denmark, Norway, Sweden, Slovakia, Finland, Estonia, Latvia, Lithuania, Netherlands, Belgium (both Wallonia and Flanders), Georgia, India, Ireland, Italy, Yugoslavia, Albania, Ukraine and Galicia, Spain, France, Russia (including Cossaack and Tatar, Turkic SSR Republics), Belarussia, Armenia, Slovenia, Azerbaijan, Bulgaria, Romania, Hungary, Luxembourg, Asian Regiment, Arab Regiment, USA (15-20 volunteers) and a small number of British troops, with the latter unit being a significant propaganda tool.

In addition to what others have said, every year more people come of military age.