I'm not management, but I've had it described to me like this: cutting soda, while it may be insignificant and certainly isn't going to change a damned thing money-wise for the company, makes the management feel better about the situation. It makes them feel like they're doing something and something is better than nothing. It's also a CYA tactic. If the CEO wants to hold somebody personally accountable, the CFO can say "look, we did everything, we even cut back the soda!"

Diversion warning: it's surprising to me how many management decisions get made solely to make people feel like they have control in a situation where they actually have no control. It's the same mechanism the government exploits when making decisions about the TSA.