happiest- I dont understand what your Rav told you. Generally, the problem is when the utensil was cleaned with hot water together with another treif utensil, not that the sponge is dirty.
Either way, not sure why you cant buy fountain soda. The soda you are drinking is cold and according to most poskim “covush” (soaking for 24 hours) wouldnt apply here.
With a coffee pot, its possible it was placed in a treif sink or dishwasher together with other utensils and now you are drinking hot coffee from it.