Water is also a solvent. It will dissolve almost anything (given enough time).

You need to use something liquid just to see what bits of the wood will soak it up and which bits have glue spots which won't. Water will raise the loose fibres in the veneer, which will require sanding down afterwards, whereas the others won't. You may want to use a water based-stain, so you only want to sand once if so.

I think all of them are likely to start dissolving/weakening the PVA glue used to hold the veneer on if you soak the veneer too much, but water probably takes the longest of them to evaporate (so is longer in contact with the glue if it soaks all the way through the veneer). So whatever you use, apply it with a rag, don't pour it onto the guitar body and then spread it around.