Which brake fluid should I use?

I'm planning to put on my summer tires next week and replace the brake pads. And since I'm already doing that, I might as well change the brake fluid. But which type should I use (DOT 4 / 5.1, ...)? I couldn't find any information about this in the manual, and the sticker on the door says "only use genuine VW brake fluid"!
Does VW have its own brand of brake fluid?

Okay, on my TDI's brake fluid reservoir, it only says to use DOT 4 brake fluid.
I guess that DOT 4 is going in there.

I've now seen it on the fuel tank and have followed the instructions accordingly. At that time, I only consulted the manual and the labels on the doors.