In principle, it doesn't have to be. But cash is theoretically the most efficient. Individuals know better than anyone else what they need at any given time. Giving them cash allows them to effectively manage their needs, and invest in their own development better than government could.

But as you said, providing for our basic needs (food, water, shelter) does not seem to be achievable in terms of cash.

Why is it that an arbitrary shortage of 1's and 0's in a computer somewhere is keeping us from achieving the end goal of UBI, which is to efficiently distribute the existing surplus of goods needed for survival that go wasted every year?