Non cc here,
I've noticed that normally non-smelly feet tend to take on a total olfactory nightmare party life when wearing synthetics for any length of time. Especially combined with a dry aircon a/c cabin miles above the earth. There is a type of natural crystal deodourant stick intended primarily for armpits; works well on feet and footwear. (Particularly effective on Teva's, should the dress code ever happen to include 'em)
The ingredient is a natural aluminium something or other crystal.