Something I posted in another thread.
Medically and pharmacologically speaking, caffeine is a central nerve stimulator, diuretic and circulatory and repiratory stimulator. Overdose will cause impatience, tremors, nervousness, easy excitability, sleep disturbance, redness of face, diuresis, irregular heart beats and such. It also causes stomach symptoms such as nausea, but there is no mention of any effect that will cause pouches to stretch.
As for soda pops. some say the carbonation causes stretching, while others consider it not good for WLS patients because it may cause one to relapse into bad eating habits from there.
The original thread is
here.
Hope this answers your Q.
Oh, and incidentally, CraigT is a secret diet Pepsi grazer.