I remember being told to be careful for the first 10 weeks, past that stage things stop effecting them as much. Coke has much less caffeine that coffee, so two cans a day would be fine.

I didn't worry too much, but I also didn't worry about listeria that much in pregnancy and both were drama free for me. It is truly personal choice.

The catch is that caffeine is "meant" to dry up your supply. In my case found the exact opposite, caffeine (and alcohol) made me produce more milk... a LOT more...