Uniformly sweet taste of Tea or Coffee is due to

Uniformly sweet taste of Tea or Coffee is due to Diffusion.
Diffusion is the net movement of anything generally from a region of higher concentration to a region of lower concentration.
The central idea of diffusion, however, is common to all of these: a substance or collection undergoing diffusion spreads out from a point or location at which there is a higher concentration of that substance or collection.