I think this is one of my greatest ideas. Its afordable, easy to make, environmentaly great, fun, and fashonable. This is my instructable for the converse contest so please vote for me.
The bottle is made of one section of bamboo with one section cut off for the cap. I used cork to fit the cap inside the bottle. Really thats all you need to know to make a bamboo bottle but I will guide you step by step.
One of the cool things about this instructable is that it requieres 100% natural materials (woohoo) so no cheating and useing artificial stuff.
Last but not least: if you feel that my bottle could be more perfect and awesome than it allready is, please coment and express your feelings.

Step 1: Stuff You Will Need

Here is the list of all the ecological materials you will need to achieve the task:
1.Bamboo
2.Silacone seel (this stuff is made out of sand and entirely non-toxic)
3.Bulliten board cork
4.Hemp
5.Sand paper
6.Pencil
7.Razor knife
8.Scissors
9.Saw

Step 2: Cut the Bamboo

This step is almost as simple as it sounds. Remember that the bamboo section you select canot have any flaws where it may leak. It should also be large enough to carry a decent amount of water (how much is up to you).
Start by taking your saw and sawing of the section you want to use about an inch away from the end of the section(I dont know what it called) be very sure your cut is level.
than cut off a section for the cap

Step 3: Clean It Out

Clean out the bottle pretty well. If you dont want the Bamboo to contaminate the taste of the water you can line the bottle.

Step 4: The Cap

For this step you need bulliten board cork. cut out about 5 or six layers of the cork uesing the bamboo as a guide.
you will than use silicone seal to glue them all togetherto make one big cork.
Now the time consuming part. Sand down the cork untill it can fit in the cap and hold it on the bottle.
glue the cork into the cap.

Step 5: In Case of Leaks

U can use silacone seal or a o ring to fix leaks out of the cap.

Step 6: Yay

you are now done with your bamboo water bottle you can add some hemp to keep the cap attahed to the bottle.
If you want you can burn kool stuff in the bamboo.
HAVE FUN