As-Salaam alaykum,

The second Ayat of Surat Ikhlas of the Holy Qur'an (112:2) reads:- "ALLAHU SAMAD".. that is Allah is Eternal and Absolute. If Allah is SAMAD, then we are the SAMADIYYA of Allah. The Samadiyya of Allah refers to 2 aspects, namely:-

(1) His Absolute Independence from all things.

(2) The Absolute dependence of all things on Him.

Thus when you lift that cup/glass to drink water, it is only BY and THROUGH the Mercy of Allah [as Rahman and Rahim] that your thirst can be quenched... this is the REALITY of things and the wisdom of our reciting the 'Basmala when eating, drinking, driving etc

The way we understand and believe affects the way we behave and act. Does water remove thirst? Does the fire have the power to burn or not? When Prophet Ibrahim, alaihis-Salaat Was-Salaam, was placed into the fire by his enemies, what happened? It became 'Bardan Wa Salaman', a place of security and tranquility.... because Allah, Subhanahu Wa Ta'ala, Creates, Controls and gives effect every single second, to every single creation, at any time He Wishes.

When we, as Servants of the Creator, say 'BISMILLAHI RAHMANI RAHEEM', we affirm the reality of things... ie that it is only by and through the MERCY of Allah, do things occur/happen, including quenching your thirst with a cup of cold water. And by our affirming this with faith in our reciting the 'Basmala, Allah then sends His Blessings (Baraka) upon the acts we do.