I'm not sure that regular green tea will be enough of a caffeine supplement to keep you from relapsing, if you're gonna go with water, meditation, all that other good stuff people have recommended then you'd better taper off soda or else you'll get the headaches that will force you back to the bottle.
Caffeine isn't what's really bad for you though, it's the syrups, carbonated water, & coloring that's really doing the toxic damage. So it's not about switching from caffeine to non-caffeine but about switching from caffeine w/ chemicals to w/o chemicals. Think of it like switching from commercial cigs to organic tobacco. You've got the nicotine/caffeine habbit both of which can be beneficial in moderation, but the western commercial administration thru cigs/soda is what's hurting you.
For a real caffeine supplement that is natural, extremely healthy, and high in anti-oxidants then I would look into guayusa. It is used by indigenous Amazon tribes right in the morning like westerners do coffee, but instead of a pick up for work like the gringos, it's a pick up to remember dreams! Not only is it one of the highest caffeine content plants in the world, it also has theobromine which can reduce physical/mental stress. This levels out so it's not a jittery caffeine like soda or coffee and it's amino/anti-oxidant activity (58μM per gram) is higher than green tea (28μM per gram) even!
Also, invest in some organic dark chocolate to control those sugar cravings! They've got a really dope dark chocolate covered goji/rasberry or acai/blueberry from Brookside Foods:
BROOKSIDE
Runa is a great company that sustainably harvests guayusa and they sell individual flavored drinks as well as a pound of loose leaf for under 20 bucks!