Coca leaves are widely used to relieve symptoms of altitude sickness in some South American countries, either chewed or brewed into a tea. Wikipedia says that no study has studied their effectiveness for this purpose, citing this as a source: https://www.wemjournal.org/article/S1080-6032(14)00257-9/fulltext
That was from 2014 and I could not find anything more recent on altitude sickness specifically, but https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3001837/ says
These experimental findings suggest that chewing coca leaves is beneficial during exercise and that the effects are felt over a prolonged period of sustained physical activity
suggesting that there could be some positive effect. Given how widely used coca leaves seem to be, I would be really surprised that nobody has studied this at all.