Can I mix some fondant with water to do some decorations on my cake (like for a bra) instead of royal icing?

I don't think it would work the same as royal.  Too elastic and water breaks down fondant (in other words, water is fondants enemy.  Why not just roll out some fondant, cut rounds with a large cookie cutter and fashion a bra that way.  Would look like fabric.

Thank you DeniseNH. I will put boobs on my cake then fondant, then paint the bra with gel color then do some decorations with buttercream