Re:2 liter prices!!!
This isn't helpful i know... but really 2-litre? 12oz cans are much fresher, I drink "alot" of soda, and maybe drink 1 or 2 a night at most. Usually can buy 3 x 12 pks for $8 or 4 x 12 pks for $11 (that's like 23cent per can) certainly alot cheaper than 99cent-129cent 2-litres that go flat quickly. (as far as per day, not per ounce) (you should stock up with the 12s are $1.99 and the 24s are $2.99-3.99, happens a few times a year at food lion and rite-aid/walgreens)
You might want to condider switching to non-diet soda. That diet stuff is very unhealthy for you with all the chemicals in it, and actually the super-sweet fake sweetners are highly addictive and make you crave sweetness more, and likely cause binge drinking/eating. You probably end up eating more calories in the long run. (plus bleck, more power to you, i'd rather drink battery acid)