Thewaterproject.org has an awesome challenge where you can pledge to participate in a 2 week challenge to drink only water. This is really something we should all be trying to do, but this challenge has a cool twist. The money you save you'll be donating to The Water Project Inc!

This is a great challenge to do because not only will it help you to become healthier, but you'll also be helping give people clean water.
Now, I only advise this challenge for those who have filters. I really don't want anyone drinking contaminated tap water to help prevent others from having contaminated water. I personally got sick the last time I drank unfiltered tap water.

If you don't have a filter then you can simply pledge to donate, not eat fast food for 2 weeks, have a bake sale, buy a filter, share this with other people, etc. Just be creative! Good luck!