The "End Diaper Need Act of 2025" aims to alleviate the financial and health burdens associated with securing essential hygiene products for vulnerable populations. It proposes to provide targeted funding to states and other eligible entities through an increase in the Social Services Block Grant (SSBG) program. Specifically, the bill appropriates an additional $200 million annually for fiscal years 2026 through 2029 to support these efforts. States will distribute these funds to eligible entities, such as governmental bodies, tribal organizations, diaper banks, and other nonprofits, to facilitate the distribution of free diapers, diapering supplies, medically necessary diapers, and adult incontinence materials. The assistance is intended for low-income families with infants and toddlers, medically complex children, and low-income adults or adults with disabilities. Funds can also be used for community outreach and to improve overall access to these critical supplies. The bill encourages the integration of these diaper assistance activities with existing basic needs programs, including Temporary Assistance for Needy Families (TANF), Children's Health Insurance Program (CHIP), Medicaid, and childcare programs. States are permitted to use up to five percent of the funds for administrative costs, ensuring efficient program oversight. Importantly, any assistance received under this program will not affect a family's eligibility for other federal needs-based benefits. To ensure accountability and assess effectiveness, states must submit annual reports detailing how funds were used, including the number of recipients and supplies distributed. The Secretary of Health and Human Services is mandated to conduct comprehensive evaluations of the program's impact on mitigating health and developmental risks. Furthermore, the bill amends the Internal Revenue Code to include medically necessary diapers and diapering supplies as qualified medical expenses for Health Savings Accounts (HSAs), Archer MSAs, and Flexible Spending Arrangements (FSAs), effective after December 31, 2025.