Using spray tan and other self tanners has many benefits. It's a much safer alternative to tanning by sun (which causes skin cancer), and if done properly creates a nice, healthy and natural looking glow. But self tanning does have its downsides--namely the sour odor that it leaves on the skin. The smell is caused by the chemical reaction that darkens the skin, and can last for hours or even days. Often you just have to ride that smell out, or try a different product next time, but there are things you can do to minimize the offensive odor.
Smell the tanning spray or lotion in store, if it it is not sealed, to find one that has the least offensive odor. You won't be able to tell the true smell of the tanner until it's already on the skin, but sniffing in advance can help. Many self tanners are advertised as not having no odor or a pleasant smell, so seek them out.
Mix a small amount of regular lotion in with the self tanner, if it is lotion-based. Many believe that this helps to dilute the smell both before application and after it is on the skin. Try to use a basic lotion with few ingredients, to lessen the chance of it interacting negatively with the self tanner.
Shower thoroughly, once the self tanner is safely set on your skin. If possible, use a body wash gel with a nylon mesh ball instead of bar soap, as it creates much more lather. Scented bath gels can also help to reduce the odor more than unscented ones.