Over the years, The Vegetarian Resource Group interns and volunteers have written articles about what vegan snacks they consume while participating in sports (think lacrosse, gymnastics, running, etc.). Here’s some of those snack suggestions:
https://www.vrg.org/blog/2019/05/13/vegan-snacks-and-meals-for-lacrosse-players/
https://www.vrg.org/journal/vj2010issue1/2010_issue1_vegan_teen_athlete.php
https://www.vrg.org/journal/vj2015issue4/2015_issue4_vegan_snacks.php
https://www.vrg.org/blog/2018/10/02/vegan-snacks-for-gymnasts/
https://www.vrg.org/blog/2016/11/07/vegan-snacks-for-a-runner-2/