Obie is Man Enough by Schuyler Bailar (MG, swimming)

The Passing Playbook by Isaac Fitzsimons (YA, soccer)

May the Best Man Win by ZR Ellor (YA, cheerleading)

Blood Sport by Tash McAdam (YA, boxing)

Cheer Up! by Crystal Frasier, Val Wise, and Oscar O. Jupiter (YA, cheerleading)

Bonus: These books all have binary trans main characters, but for a nonbinary athlete, check out Ana on the Edge by AJ Sass (MG, ice skating)