The reason sugar won't wash away as easily is it will already be sticking to other things in the pipe.

Sugar has hydrogen bonds so any small amount that does dissolve in the alcohol will readily stick to other things.

Sugar will also easily dissolve with any water already in the pipe.

Once sugar has stuck to other things it may technically no longer be sugar but it will still be there.

Salt might react but generally the NaCl bond is pretty common because neither readily reacts with much else.

Flourine from any fluorides around maybe and heavier earth metals but generally, and water and the ions will just stay pretty close to each other in solution.

Hydrogen bonds like other hydrogen bonds and lots of stuff has hydrogen bonds.