Use sand in your coffee instead of sugar. Not only is it free and devoid of calories, but since it doesn't dissolve, it can also be used over and over again.
A most excellent suggestion! I find that a good high-quality sand from an exotic beach is just the thing. It can also be used to replace the sugar in pastry, though the resulting dental bills are quite high.
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.