Why is it that HIV virus can not live when expelled in a sneeze?

Why can't it be transfered to another individual via saliva?

It is probably a combination of the fact that HIV does not fare well in saliva along with the fact that arial transmission is unlikely to put the virus in contact with the specific types of white blood cells that HIV infects. There is one supposed case of HIV transmission through saliva, but I'm not sure that was ever confirmed.

I've read that it doesn't survive outside the body very well.

Most, maybe all viruses need a host to get by. Malaria and many other pathogens are using the mosquitoes to spread and find new hosts.

Others go by blood-blood contact (like HIV of course), some by pray that has been infected.

If viruses could spread by air, we could be in trouble. Additionally, strange as it may sound, HIV is killed in the mosquito body by its own defense mechanism. If HIV could find a way around this problem, this would be a read disaster for human kind.

HIV as all viruses are themselves not allowed. They come to 'life' by hijacking the DNA of cells. Even simple bacteria can get ill by them. They can 'sleep' for a long time and suddenly come into action, invading the body in huge numbers, making the host very ill in most cases.

HIV has been found in saliva and tears in very low quantities from some AIDS patients. It is important to understand that finding a small amount of HIV in a body fluid does not necessarily mean that HIV can be transmitted by that body fluid. HIV has not been recovered from the sweat of HIV-infected persons. Contact with saliva, tears, or sweat has never been shown to result in transmission of HIV.

Some people fear that HIV might be transmitted in other ways; however, no scientific evidence to support any of these fears has been found. If HIV were being transmitted through other routes (such as through air, water, or insects), the pattern of reported AIDS cases would be much different from what has been observed. For example, if mosquitoes could transmit HIV infection, many more young children and preadolescents would have been diagnosed with AIDS.

HIV, like most other pathogens, cannot survive outide the body for very long. it needs the right environment, and outside of the body is not conducive.