Tribal Nutrition Improvement Act of 2018 This bill amends the Richard B. Russell National School Act to allow an Indian tribe to assume, from a nearby local educational agency (LEA) and in lieu of a state, responsibility for administration of the school breakfast program, the school lunch program, the child and adult care food program, or the summer food service program for children. The Department of Agriculture (USDA) must identify, for optional use in LEAs on or near Indian reservations, alternatives to current program requirements related to the daily counting of meals by category, the use of annual applications to determine program eligibility, and the use of universal meal service. USDA may implement such alternatives, as limited by the bill, as well as further test them in demonstration projects. The bill also amends the Child Nutrition Act of 1966 to require USDA to increase the amount of administrative funds paid to an Indian tribe that agrees to assume responsibility for the administration of one of the aforementioned food programs.