Want a fun, profitable, healthy experiment to run for a month?
Try drinking only water.
I've switched onto "Water Only" a few times in my life. I'm running it right now. It's terrific.
The merits of the policy:
-- No liquid calories and all the downsides that come with those: unless you're playing sports or doing heavy manual labor, liquid cals basically come in two forms: bad and worse. Merely bad liquid calories are things like juice that have some other micronutrients. Why are they bad, then? Because you're missing out on all the fiber and satiety that comes from eating that apple instead of drinking apple juice, and -- again if you're not getting lots of fitness -- the spike in blood sugar, followed by insulin, leads to a crash. And that's juice, which isn't all that bad. The "worse" is Coca-Cola and similar stuff that really ought not to be put in the human body if you're aiming for mental and physical performance.
-- You might be staggered if you calculated how much you're actually spending on beverages; at least, I was. My spending on coffee, tea, and other drinks was $500+ per month -- and heck, I haven't drank alcohol this decade. So that leads to having more cash, which leads to the second point...
-- I don't believe in deprivation and mindless asceticism; rather, I believe in getting the most out of one's life. Once I did the math on my spending on beverages and cut it, I resolved to redeploy that spending to gear I wanted to buy anyways. Believe it or not, the net savings from beverages were redeployed such that I could buy: a fantastic pair of Frye leather boots, a new top-of-the-line iPhone, a special forces grade backpack that's great for hiking/marching/traveling (but also looks very business-casual-ish and goes fine in the boardroom), and -- wait for it -- a new Macbook Pro. Yeah, it's amazing how $3 to $15 per day adds up thousands of dollars over time, isn't it? I bought a bunch of cool stuff that's much more enjoyable and life-enhancing than some beverages which, once guzzled down, are gone.
-- I try not to do liquid calories anyways, but if you were doing liquid calories, why don't you just eat ice cream? You can get some great ice cream bars for like 70 to 200 calories per ice cream. If you want the indulgent calories, why not get the max enjoyable calories?
-- And finally, the biggest and bestest thing from this policy is my caffeine regulation gets much better. I love coffee -- I mean, I really love it -- but I'll often drink coffee too late in the day, or have too much of it during a work session. Coffee is obviously way better for you than cigarettes, but it works in a similar way: it's the mix of the stimulant (caffeine/nicotine, respectively) when combined with the pleasurable tactile activity (drinking coffee, smoking). Meanwhile, 100 mg caffeine pills are the equivalent of a single cup of coffee and cost somewhere from 3 cents (cheapest countries) to 20 cents (buying them at the airport in a massively expensive country)... and I feel no inclination to over-do them. As such, it becomes very easy to exactly regulate caffeine usage.
-- This regulated caffeine usage means better working, and much better sleeping. If you're a heavy caffeine user and ever have problems falling asleep, ever, you really owe it to yourself to try a mix of water or herbal tea for a while with caffeine pills, carefully regulating your dosages. You'll have more energy, less jitteryness, get the positive effects of caffeine, but sleep better. Oh yeah, and your wallet will be fatter with which to buy other things.
I've done a few Water Only cycles. It's very hard for a week or two, and then trivially easy once established. If you're productivity-inclined, give it a whirl on a one-month trial and see how it works out for you.
Bottle of water, omelette, and Japanese 100 mg caffeine pills to start the morning. Note that buying a fancy omelette at the airport restaurant negates some of the monetary benefits of Water Only -- the productivity and caffeine regulation do still apply!
Oh, final bonus? Very easy to take caffeine immediately upon waking in this form, meaning faster wakeup-and-get-going to start the day. It's only 20-30 minutes, but those are 20-30 morning minutes, the most valuable kind.
Let me know if you give this a whirl; it's hard at first, but then easy, and I've found it very beneficial.