Apple vinegar has a distinct smell when the bottle is first opened, but in a leave-in spray the scent usually fades as the product dries. The formula also contains aloe juice and yeast extract, which are not strongly scented, and the product likely includes a fragrance to mask the vinegar note. In practice, most people do not notice a vinegar smell after the hair dries, but this can vary depending on how much you use and your sensitivity to scents.
If you are concerned about the smell, start with a small amount and see how it feels on your hair. You can also apply the spray to damp hair and then blow-dry or style, which helps the scent evaporate faster. If your skin is very sensitive to fragrance or acidic products, it is sensible to test the spray on a small area of skin before using it on your scalp. The acidic nature of the vinegar is what helps smooth the cuticle, but the amount in the spray is low and meant for leave-in use.
If you find the smell too strong, you can use the spray only on the lengths and ends, away from the roots, and rinse your hands after application. The scent typically does not linger on the hair for a long time.