Breast sweat can be uncomfortable and irritating to the skin, and some may stop you from sweating, and deodorants mask the smell of sweat.
Like other yeast infections, itching, burning, and pain at the rash site are common symptoms. Breast yeast infections can give off a bad odor, too.
It makes sense if it works for your underarms, applying deodorant under the breast can help to reduce sweat and odor there, too.
The Women's Guide to Care and Maintenance of Yourself doesn't include a chapter on how to get rid of smell between breasts. This unfortunately.