what german sweet maker runs a gimmick where kids can exchange acorns for sweets?

The German sweet maker you’re looking for is HARIBO.

In Germany, HARIBO runs a long‑standing autumn promotion where children can bring in collected acorns and chestnuts and exchange them for HARIBO sweets. This tradition dates back to the 1930s and still takes place today at their site in Grafschaft (and historically in Bonn), with many tonnes of nuts collected each year and then used, for example, as animal feed in winter.

So, to answer the question directly: HARIBO is the German sweet maker with the acorns‑for‑sweets gimmick.

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