Surface Color and Volume Absorption

I see you still have a rather strong surface color. In reality, liquids are not really colored by light loss on the surface, but ligh loss within the material. You should leave the color of the surface shader white and use the color for the absorption. The gradient may or may not be needed based on your initial intent with it. Experiment with the density of the absorption.

Refraction and Transparent

I am not sure why you mixed these two shaders. You should get a better result with simply a glass shader.

For Full Realism

You should note that only one surface should be between the glass and the tea and that should be a third material, with an IOR of IOR-tea / IOR-glass. This applies also for the ice cubes. This also means that the meshes will not be manifold, but this is how the render will be most realistic.

These are useful to read:

• fluid in a glassfluid in a glass
• Liquid / glass interface IOR and normals in CyclesLiquid / glass interface IOR and normals in Cycles
• http://adaptivesamples.com/2013/10/19/fluid-in-a-glass/

Alternative Solution

You can use the ray length to calculate the correct absorption, but this was useful only before cycles volume shaders was implemented:

• http://blenderdiplom.com/en/tutorials/419-tutorial-absorption-in-cycles.html