Water is fairly ubiquitous where humans live since humans need it. It might not be a lot of water, but if humans live there, then there must be some water.
In the early church when it came to baptism, the preference was for "living water," i.e. flowing water. But we can see them making exceptions for those who didn't have flowing water, e.g. a stream.
"But concerning baptism, thus shall ye baptize. Having first recited all these things, baptize in the name of the Father and of the Son and of the Holy Spirit in living water. But if thou hast not living water, then baptize in other water; And if thou art not able in cold, then in warm. But if thou hast neither, then pour water on the head thrice in the name of the Father and of the Son and of the Holy Spirit. But before the baptism let him that baptizeth and him that is baptized fast, and any other also who are able; And thou shalt order him that is baptized to fast a day or two before.” Didache 7:1-4 (c. 60-100 AD)
Obviously, it's the same element, but adjustments were made for need. Perhaps one should abstain if no bread and wine are available. In dire circumstances, if one used crackers and water, I seriously doubt any harm would be done so long as the hearts of those partaking are right, which in dire circumstances they likely would be.
At the end of the day, I don't think God's grace is bound by the sacraments. The sacraments were created for humanity; humanity was not created for the sacraments. Likewise, the sacraments are not magic, but means of grace, which again is not bound by our performance. If one can receive grace without the sacraments, then to use what is available (again, in the most dire of circumstances) would hardly negate the grace that is available without the sacraments.