I generally go fairly light on the sauces and such, so I voted Never. Considered a test bite, but I'm pretty sure that once I saw the test bite, I'd decide to skip it.
I have been known to combine beverages at times, but not everything available. I'll add a splash of peach tea to an orange soda, or if the smoothie choices are orange-pineapple and strawberry-banana, get half and half since all four of those go well together. Generally though, it's something that will probably go well, not adding things for the sake of adding them.
Not a fan of milk in tea. Although I may be doing it wrong. So far I tried tea + a bit of milk, and it was an unpleasant experience. I've seen some people do mostly milk, and brew tea in the milk (and then cool it?). Perhaps that would be better. But currently I'm fine with tea as-is, without any additions.