Sugar Policy Modernization Act of 2017 This bill amends the Federal Agriculture Improvement and Reform Act of 1996 and other agricultural laws to modify the Department of Agriculture (USDA) sugar program. The bill modifies the sugar program to: reduce the rates for price support loans to processors of domestically grown sugarcane and sugar beets; require USDA to recover the net cost of the program from domestic sugar processors; extend through 2019 and then terminate the Feedstock Flexibility Program under which USDA purchases surplus sugar from domestic processors for resale to ethanol producers; extend through 2020 and then repeal the flexible marketing allotments which limit the amount of sugar that domestic processing companies may sell for domestic human use; require USDA to administer the program to provide adequate supplies of sugar at reasonable prices; require USDA to adjust sugar tariff-rate quota imports to achieve specified ratios of sugar stocks to total sugar use; and allow the transfer of quotas between countries.