I know 10 2 4 was embossed on Dr. Pepper bottles... and used in their advertising to show the time of day the body needed a pick me up to avoid an energy slump. I think their motto was something like drink a bite to eat?
i've never seen it on pepsi bottles ..just early dr. peppers...i agree with California on the meaning of the numbers but never heard the "drink a bite to eat" ?
Googled it and found this:
After Dr. Eddy’s research findings were released, Dr Pepper challenged its advertising agency to come up with a theme which would suggest that Dr Pepper should be that 10, 2 and 4 drink which would keep the energy level up. The result was one of the most enduring of Dr Pepper’s advertising themes: Drink a bite to eat at 10, 2 and 4.