If you really want it, you will achieve it. Get support and slowly you will start to reach your goal. Don't give up. In some cases, people start doing well on the first day, second day, third day, and then let's say on the 4th day they had snacked on a cookie..okay so now they feel hopeless and or stressed. They start to "believe" that they ruined their goal and so they start to consume all these regular treats. Then you have to start all over and the cycle begins. I've been in that cycle. It's really hard especially since our body and mind is used to the sweets, sugar, and high on fat food/drink.
Now a 30 day goal is good. Though if you what to eat healthier, go on a run daily, and drink only water then shouldn't that be a lifestyle for the rest of your life? All your hard work can be gone after the 30 day.
Everyone starts off slowly and will make mistakes but don't pound yourself on it(:
As for only drink water, you can add flavoring such as those packets or droplets, add a lemon, or even so make your own detox drink (anything that's a fruit or vegetable..just throw it in there). Another way to help cleanse your body is like warm water with a bit of sea salt (I wouldn't consume this as a daily task). It takes time so don't rush any process. I have been at this trying to eat healthy and working out for a month in a half (now I did have my bad moments but I had slept decreased my income of sugar). I no longer eat unhealthy pizza, eat take-outs such as fast-food, candy bars (though it won't hurt to have a bit of chocolate in your life). All this food accordance will have to be up to you and what you decide to eat (this over that). You don't have to be a pro to have that perfect healthy meal plan. There is several plans on how to have a better lifestyle.
I recommend looking it up. Do it for you.
As for running daily, it's understandable if one wouldn't be able to get in a run(work, school, time itself just flies on by, etc.)
Even just moving around the house or at place is allowing your body some good. Don't focus too much on this everyday where you forget about other tasks. It will come in naturally if you really want this.
You CAN do this!