equal parts Baking Soda and Cornstarch mixed. Add a few drops of Essential Oil if you prefer. The baking soda neutralizes odors while the cornstarch absorbs excess moisture. (It's natural to sweat! It's also healthy)
The essential oil just gives a pleasant scent throughout the day.
Tea Tree Oil rubbed underarms works wonders! It's a natural antiseptic and once the initial strong smell wears off you're good to go!