Salt formation has been extensively used to improve drug properties, including solubility, stability and mechanical properties. A sweet salt of metformin with acesulfame, prepared though an anion exchange reaction, showed superior properties over the commercial hydrochloride salt. These included both remarkable improvement of taste and significant enhancement in tabletability, which is explained by the different crystal structures and lower hardness as measured by nanoindentation. The relationship among crystal structure, mechanical properties and tabletability was rationalized through an energy framework analysis. This approach led to the successful development of an orally disintegrating tablet product containing 60% of metformin-acesulfame salt by direct compaction.