Can I re-apply a week after being denied?

I am a Philippine passport holder and my sister's visa application has been denied today. She already has plane ticket and would really like to be granted a Tourist Visa. We have an uncle who is a permanent resident in Japan and is willing to give us sponsorship documents. Is it possible to re-apply for a new visa after a few weeks but this time, she will be applying with a sponsor/guarantor?

As far as I know, there is a guideline that says if the circumstances have not changed, you cannot apply within a few/several months. But in her case, since she now has a sponsor/guarantor (and she did not have him as a sponsot/guarantor in the earlier application?) then it might be accepted. For official answer, yes, check with the embassy.

Probably, the reason for the denial was not the lack of a guarantor, but the risk that she would seek to work illegally and/or overstay. It is important to demonstrate strong ties in the Philippines, such as employment. If anything, having ties in Japan such as family is a disadvantage here, since it gives an incentive to stay.