Dr. Pepper-
Hmmm… – that’s a possibility I hadn’t thought of (a mark at the two-gallon line of one of the five-gallon jugs). But, the answer is no – you have no way of marking the jugs, be it a scratch, dent, stain, etc.
Here’s a hint – environmentalists won’t like the solution.
blueberrymuffin-
Hi.
I may be missing something, but based on your question, it doesn’t seem to matter which day it is – just take one from each jar.