One add-on that every MacBook (or PC laptop, for that matter) needs to have is about a two foot stick beside the keyboard. Anybody who comes near with a drink, gets wacked on the hand that isn't holding the cup.
That is only a partial exaggeration. In my frequent use of Internet coffee shops, I use my own spill proof cup with a crew on lid.
In an earlier career of fixing all kinds of IT equipment, from keypunches to PCs, this is my experience...
Water, black coffee and non-sweet tea are the best, to use the word 'best in a backward meaning. They aren't conductive to any extent, so assuming that they don't literally soak some critical open component, no damage will probably be done. Just set the machine in front a a fan for a day or so and it will probably still work. As cwa107 said, it is a crap shoot.
Sweet coffee and tea have have the same effect and probably won't blow electronics. But, and it is a large butt, the sugar can absolutely ruin a keyboard. By ruin, I don't mean destroy, but it will stay tacky from humidity to the end of time and you will have keys that are constantly sticking. And since sugar is not dissolvable by any usually available non water based solvent, you can't get it out. A very few times, I have had success in immersing(!!) the whole keyboard in clean water and rinsing, followed by a two day drying period. This option is obviously not available for your laptop.
Soft drinks are the worst. Not only do you have the sugar problem squared, but the phosphoric acid and other highly dangerous junk in the drinks not only short out pins and lands on the boards, but continue to corrode them over time. (In the interest of full disclosure, I am addicted to soft drinks like every one else. Just not near my immaculate Air.)
I can't remember ever successfully recovering a coke soaked keyboard.
