WARNING: This page is about a different car, the 2006 Audi A4, 2005 Audi A4, 2004 Audi A4, 2003 Audi A4, and 2002 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Special Tools - Coolant, Draining And Refilling
Courtesy of VOLKSWAGEN UNITED STATES, INC.
Special tools and equipment
VAG1274/8 Adapter
VAG1274/10 Adapter for VAG1274 Cooling system tester