Any DIY (Do-It-Yourself - usually in the comfort of your home) is the best and when they involve a mix of things that work and don't harm the body even better.
A lot of people are battling dark underarms as a result of ingrown hair, shaving the wrong way and many more reasons making them shy away from donning any look that would reveal that bit.
A simple DIY works for this and it's tried and tested; using the ever dependable baking powder (which works a lot for beauty purposes apart from baking), corn starch, the miracle coconut oil in a simple way to get rid of the embarrassing dark underarm and the best part is it keeps you smelling great!
Watch and learn in short easy steps above.