The staples of Thuringian cooking — schnitzel, sauerbraten, bratwurst, potatoes — are well represented across the city. For traditional regional food, Feuerkugel (Fireball) in the city center is a reliable choice at reasonable prices. Tipping is not obligatory but rounding up to the nearest euro is the local custom.
The cheapest meal in town is the 1-euro bratwurst sold from stands in the city center — don't miss it. Döner kebab is also ubiquitous and popular with locals. For fast food eaten the Erfurt way, note that french fries come with mayonnaise, not ketchup.
The city hosts a farmers market near the Dom, where vendors from across Thuringia sell bread, bratwurst, fruit, vegetables, and more. It's worth timing a morning around it.