"Spit" achievement is one of the most difficult because it's totally random.
here is case of a friend

Click image for larger version.  Name: spit in final 2.jpg  Views: 148  Size: 67.6 KB  ID: 40243

it's just happened.

I don't have mine but it was in a game, I was winning 1-0, then the oppo manager start watching the game and all of a sudden my player spits on another. This is something that happens, I mean if the oppo manager is coming in the game, something is happening. There is a reaction in the program.
Anyway, I was happy I get that without hunting it or loosing anything.