I have a 1 litre water bottle at work and I put 3 elastic bands around the bottle. Every time I empty the bottle I remove a band. Once I take the last band off, I'm done for the day. That's my trick for work. At home, I fill a 1 gallon pitcher with water and keep it in the fridge, and when I'm down to under 1/4 of the jug left, I've had my quota for the day. Works for me....

N.