Disclosed are a fuel unit for a hydrogen generator and methods for producing the fuel unit and the hydrogen generator. A fuel sheet (50) is made by disposing a plurality of fuel pellets (50A-50J) containing a hydrogen-containing material on a substrate (52), and one or more fuel sheets are formed into a non-cylindrical fuel sheet assembly my moving (e.g., bending) a portion of the fuel sheet (50) to position pellets adjacent to each other such that adjacent sides of the adjacent pellets lie in essentially parallel planes. A non-cylindrical fuel unit is produced from one or more of the fuel sheet assemblies. Fuel units can be replaceably disposed in a hydrogen generator, and fuel pellets can be selectively heated to produce hydrogen gas as needed.