Agree with posters above; my DD did not bring cleats and has never needed them. If you are in a sport that needs them, then of course bring them. The 2025 Appointee book on the website shows cleats are on the packing list. Regarding undergarments, DD felt more comfortable bringing all white, but I agree you can bring other colors, especially if you have worn undies now that will get trashed during BCT. For ladies, just remember you will be wearing white shirts, so white/nude/flesh tone might be a good strategic choice there.
Candidates will likely have their own slack or social media platform to meet and ask each other questions. I don't know exactly what DD was on last year, but got a lot of good information. Reminder: you always want to project the educated, literate officer you aspire to be.
From others on that slack (or whatever that platform was) I do recall she was surprised even with careful attention to the Handbook, she missed something - it's in the 2025 Appointee Handbook, page 4, section on The Armed Forces Officer Reading Assignment Instructions. I also recall she thought it was very dry, and Cadets might want to chime in whether it's a critical reading item. I don't know, all i'm doing is citing DD's experience and what was in her 2024 Handbook and the current cycle's as well.