Diphenyl and methyl phenyl sulfones and sulfoxides and dibenzothiophene sulfone were treated at 460 °C with water, 15% aqueous formic acid, and 15% aqueous sodium formate. Thermal comparisons were run in cyclohexane, and for those compounds and conditions that resulted in fast conversion after 7 min at 460 °C, also at lower temperatures. Sulfoxides are highly reactive, sulfones less so. Reactivity is greatest in 15% aqueous sodium formate followed by formic acid for the sulfones; this reactivity order is inverted for the sulfoxides. In all of the aqueous media, ionic reactions dominate. The sulfoxides are mainly deoxygenated to the corresponding sulfides, while C−S bond cleavage is more important for the sulfones. Product slates are identified and analyzed, and reaction pathways are suggested for the transformations found.