A person is trying to keep away from soda. However, the person does not feel as satisfied with drinking water or seltzer. Regarding Birkas Ha-Mazon a satisfied feeling should be had. Can this person make Bircas hamazon even though he lacks satifaction from water during the meal? Should he avoid eating bread? What about on shabbos?
He can recite birkas ha-mazon as usual, and does not need to avoid eating bread.
Although the Rema (197:4) mentions the opinion that if one feels thirsty, and does not drink, the Torah obligation of birkas ha-mazon is not incumbent, this won’t apply in the case of the question, where the person does not feel “as satisfied” with water as with soda.
Although soda might be more satisfying, the satisfaction of water — meaning, quenching thirst — is sufficient for the full obligation to apply.
In addition, even where the Torah obligation does not apply, there is at least a rabbinic obligation to bench.