If this is your first shake'n'bake cook consider the phrase, 'READ ALL INSTRUCTIONS COMPLETELY BEFORE PROCEEDING' to be relevant here and threads like these to be the instructions. You will understand what is going on a whole lot better by doing so and possibly avoid a catastropohic accident.

A capful of water is insanely too much - all it takes is one fucking drop to ignite your Lithium and put you in serious fucking danger. Just google search 'one pot method meth fire explosion shake' and read the newspapers about it. It has happened a lot of times and isn't a joke. Most people never add any water and everything is fine

These instructions are weak and don't tell you shit about what is really happening here anyway actually: hence, keep reading and researching.