This is in many ways a hard question to answer, ATP is the energy currency of many cells, in that it is the way energy is used by many enzymes. But it isn't very stable, in bulk, or in solution. You can buy a vial from chemical supply companies, and keep it on ice, and make a solution of it, to add to a tube of isolated enzymes, and run a reaction. But it isn't easy, to get enough into solution, for a long enough time, to keep cells alive. It'd be a pretty expensive experiment, to prove ... not much at all.
As for the taste, many nucleotides are used in trace amounts as flavor enhancers in prepared foods. Just like free amino acids, like the monosodium salt of glutamic acid (do you know that one?) they add an umani flavor to foods.