a private agreement reached between a public agency or government official and a private company that includes illicit payments or special favors. They found that the mayor was involved in a number of sweetheart agreements. Most of the building contractors in town would be out of business if they didn't have sweetheart deals with the local politicians.
n. a deal made between friends so that both may profit well. (Such deals usually involve illegal or unethical practices.) Most of the general contractors in town would be out of business if they didn’t offer “sweetheart deals” to the politicians.