Manufacturers claim that they are absorbed into the body faster and in a higher dose than pills.
Vitamins delivered through a spray into your nose or mouth are being heavily promoted. They're hyped up as being easy, efficient and best for your body. I haven't seen any evidence that spray vitamins are better absorbed, though. They certainly cost a lot more money, and I don't think they're worth it. When you inhale it in a nasal spray, it passes directly through the mucous membranes into the bloodstream.