I saw this pin: http://www.pinterest.com/pin/365706432212677393/ The one where you cut open an Energizer battery and find it is made up of watch batteries.
I've been meaning to see if this works for a while, but didn't have any Energizer batteries, so I tried it with a Duracell and a Sony battery.
The first one is the Sony and the second one was the Duracell (which was a bit leaky :-/). As you can see, neither of those brands are made up of the smaller batteries. They had both run out, so I didn't waste a battery. If I happen to come across an Energiser battery that has run out, I will open it up to see, but it did say on the pin that you must use that brand and model and that they couldn't guarantee any other brand, but I wanted to have a look to see anyway =)