Some resources for skinny guys like you:
www.36pounds.com - a blog for skinny guys who want to gain muscle (you will find a lot of info there specifically for skinny guys)
www.johnberardi.com - a great specialist of nutrition
I don't drink anything during a workout. Just after.
At that bodyweight you don't need abs workouts cuz they will show up pretty fast for you. Better focus on serious exercises like squats and deads. Here is a good program:
http://www.36pounds.com/2009/04/28/36poundscom-beginner-workout-program-for-skinny-guys/
Best of luck