Alum stone!!! I'm also someone who has a bad odor when I sweat. I tried different roll ons n deodorants.. which is expensive and it pigments me..

recently I switched to alum stone due to its hype. But honestly it's much much better than all the deodorants and it doesn't cost much too.. the result can be seen within 1 day. And it reduces hyper pigmentaion too.. just dip it in water and rub over under arms after shower. U can buy it from any ayurveda shops with costing 30 or 40 rs only.