This expression means; It’s the moment of truth!

This phrase is used during a moment when you need to give it
everything you’ve got, whether it’s a competition, a game or a job
interview. The use of the sausage relates to the historical importance
of sausages in Germany. This phrase was first documented in Leipzig
in 1881, but its origins are thought to date back much further.
Throughout this period in Germany, fairs and festivals were
becoming increasingly popular in towns and villages across the
country. Many games and competitions would offer large and
high-quality sausages as the winning prize. Unlike today, sausages
were a high end and expensive food that could easily be worth a
week’s wages for someone of a lower class. Winning a sausage prize
would be a great honour and treat for the family, allowing them to
share a delicious delicacy that they wouldn’t normally be able to
afford.