Have I had to do it?
I don't do anything else!
for example, my drink of choice was/is whiskey. It comes in 2 size bottles - 70cl and 1 litre. The smaller has 28 (UK) units, and the larger has 40 units. I just estimate how many I've drunk. Lets say I start a 1 litre bottle on a Monday. I estimate my consumption at 8 units, 0, 6 units, 9 units, 6 units and 7 units over the next 6 days, at which stage the bottle is finished. I add up the units and get a total of 8+6+9+6+7=36. I know the bottle contains 40 units, so I'm out by 4. I need to add those 4 on to the above consumption. I'd probably make it 9+7+10+7+7=40
If I start a new bottle on the night I finish an old one, I'll estimate how many units I drank from the new one.
No need to sweat it too much as the accuracy looks after itself over time.