The most distinctively local food experience in Hveragerði is rúgbrauð, the dense rye bread that is baked underground in geothermal pots. Restaurants and bakeries in town serve it alongside smoked Icelandic lamb, salted butter, and pickled fish — a combination that has been the standard local meal for generations. The bread has a slightly moist, sticky texture from the long slow cook, and a faint mineral character that you do not get from oven-baked versions.
Geothermally grown vegetables from the town's greenhouses also appear regularly on local menus. The tomatoes and cucumbers grown here have a different quality from the imported alternatives found in Reykjavík — sweeter, with more flavour — and when they are in season they are worth ordering. A few cafés serve soup made with local vegetables alongside the bread, which is a straightforward but genuinely good lunch.
Skyr — the thick Icelandic dairy product that sits somewhere between yoghurt and fresh cheese — is available everywhere in Iceland but is locally produced by several farms in the south. It is eaten at breakfast with local berries when in season, or as a dessert with honey and cream.