I suffer a lot with this, mainly towards the end of a long heavy session, but also 1 to 2 hours after the session. Electrolyte tablets help quite a bit, ( 2 pre, during if feel onset, then 2 post workout). I also have a couple of Bananas pre workout and have a good multi vitamin.
I agree too much fluid ( water ) can be as bad as too little ... its the concentration of electrolytes that is key. I feel that my post work out cramps maybe a result of drinking plenty during workout then suddenly stopping, so water consumption is now gradually tapered off post session - ie don't drink shit loads then nothing after the session!
I also feel cramp is related to recovery for me at least ... too shorter recovery will make me more prone.
Hope this helps.