The 1921--1924 hyperinflation happened mainly because of three things: the ongoing internal political instability in the country, the occupation of the Ruhr district by foreign troops, and when the Weimar (modern-day Germany) government printed too much banknotes to pay reparations after the 1923 French invasion. Because the banknotes were not matched by Germany's production, their value fell.

In 1922, a loaf of bread cost 163 marks. By September 1923, during hyperinflation, the price crawled up to 1,500,000 marks and at the peak of hyperinflation, in November 1923, a loaf of bread costs 200,000,000,000 marks.

Cash being prepared for burning

Cash being sold by weight

Kite made of banknotes

Bread price: 4.60 million marks

Cash being transported to pay salaries

German children build a pyramid with stacks of inflated currency

Carrying cash

Dress made of cash

Cash used as fuel

1000 billion mark note

H/T OldPicsArchive