Fair Trade in Grain Act of 1993 - Requires a consignee of imported foreign grain to: (1) include an end-use certificate in the documentation covering the entry of such grain; and (2) submit to the Secretary of Agriculture certain quarterly reports regarding the use of such grain. Sets forth civil penalties. Prohibits the Commissioner of Customs from permitting the entry of such grain unless the importer of record presents such certificate at the time of entry. Amends the Agricultural Trade Act of 1978 to require the Secretary to provide agricultural commodities or cash payments, or both, to promote U.S. wheat exports to Mexico. Directs the administering authority to initiate a countervailing duty and antidumping duty investigation with respect to Canadian subsidies for wheat exported to the United States.