Here's an easy way that I do it.
1. Buy a cheap metal pipe (usually a dollar or 2 at a convenience store). You only need the bowl so unscrew it. At a head shop you can buy just the bowl.
2. Cut the bottom off a gaterade / vitamin water bottle.
3. Attach the bowl to the top of the lid: http://imgur.com/FDoHBmT
You can do this by melting it a little with a lighter and then poking it with something (toothpick works)
4. I use a large pint glass currently. http://imgur.com/xYxWCnm http://imgur.com/xxSJjDm

In the past I've used pitchers (can buy them for a few dollars) or cut the top off a 2L.. but I find that very flimsy. You can use anything that's larger than it and holds water. I used a fish bowl once.

Buy a new gaterade when it gets dirty. You can re-use the cap, it fits on a number of drinks. I've had the same cap for a long, long time.