Start in the bath! Not as crazy as it seems - might not work though. DS practices drinking from a cup in the bath - I try to make sure its clean water, not the bath water but some bath water gets swallowed.

I give him a cup with just a tiny amount sometimes when he sits at the table and don't worry too much if it spills (and don't react to avoid the game of spill the water so Mum freaks and cleans it up)