Can i apply for US visa until i get to apply for green card?

US consular officers aren't paid to help people fulfill their destiny. Their job is to give visas to people who qualify for them. A tourist visa is legal permission to visit the US. A student visa is legal permission to study in the US. These visas do not permit people to overstay and live and work illegally while trying to get a green card. Because so many people fulfill their destiny by using tourist and student visas to immigrate to the US ahead of family members patiently waiting years for immigrant visas, US consular officers require applicants for temporary visas to show strong ties that reduce the chance of overstaying a visa. Don't blame US consular officers for doing their job. Blame people who live and work illegally on expired tourist and student visas, making it harder for legitimate visitors and students to get approved. You can certainly apply for a tourist visa, but if you've been denied once and circumstances haven't changed significantly, i.e., you haven't gotten married or found a great job, then you're likely to be refused this time, too.

If you got denied you will be denied again. It will take 20 years for her to sponsor you.

You dont bother to give your country so cannot comment without information

To begin with it would help to know where you live. There are places where it is virtually impossible to get a US visa. Also, they didn't deny you for "no reason". There was a reason and if you don't know what it is you're not going to get much help until you find out what that reason was. Edit: Intentionally or not your sister bent the rules to obtain legal residence and immigration expects you to try to do the exact same thing. You can expect they will never give you a visitors visa for that reason. Your sister can't sponsor you until she becomes a citizen and even then her sponsorship doesn't carry much weight in getting you a green card. Her sponsorship would help but it will still take years. To get a green card quickly you need to be sponsored by a parent who is a citizen. You're probably going to be limited to getting a green card through the normal channels, the lottery, a professional degree that is needed in the US, investment of $500,000 in a US company or real estate..

Getting your visa to visit won't affect anything after your sister submits for your green card, but she don't have to wait until she becomes a citizen she can apply for you now which would be best since it takes ten yrs to get your green card and having the tourist visa is a plus, I recommend for you to find out what is the reason they keep denying your visa petition maybe your sister and brother in law need to make a letter requesting you and assure them that you'll be taken care of once you're in the states! Good luck!!