I know im supose to use DOT4 but is there a specific brake fluid for bikes or can you just use anything???

I am using the Motul RBF 600, it is rated pretty good and has a higher boiling point than some of the others.

anything but synthetic.

I will use Motul Synthetic when I change my brake lines to steel braided. If you change to a different DOT # fluid, make sure to completely drain &flush the whole system. Some are not compatible with othersand can crystalize causing brake lock-up. When you flush it, use brake cleaner. Also use a new sealed bottle of fluid & be sure to bleed it really good before and after the test ride.