Honestly forget the overpriced tourist markets near old town square

Havelské tržiště has real vendors selling proper czech street food for locals not instagram photos. Try the klobása stands - thats actual czech sausage with proper snap when you bite it, not the mushy tourist versions

Also the trdelník but ask for less sugar than they usually put on tourist ones. Markets get busy around lunch so go before 11am or after 2pm