Military Nutrition Improvement Act This bill requires the Government Accountability Office (GAO) to conduct an assessment of the quality and nutrition of food available at military installations for members of the Armed Forces. The assessment must include specified elements, including a description of the extent to which data is being collected on the nutritional food options available, including the fat, sodium, and fiber content of hot line foods. The GAO must brief Congress on the status of the assessment and submit a report on the assessment within one year after such briefing.