Mix curry powder with tomato ketchup 'til you get the mix you like. You could add salt/pepper, chili, cayenne, sugar, onion salt - no real rules to it.
Pour over your bratwurst - chopped up, or not - and add chips and a baguette for the full hit.
Or buy a bottle of curry ketchup and do the same.
Berlins proud addition to the world of gourmet street food . . . . .