Effect: 

A participant sips ordinary water from a cup, and is able to taste what a second participant is drinking. 

Conditions in place: 

1.) The participant can feel and sniff inside the cup, making sure nothing has been added. 

2.) You never secretly drop anything into the water. 

3.) They can drink the water BEFORE and AFTER the taste changes. 

4.) Neither the cup, nor the water, is ever switched. 

An alternate presentation is also taught, which will allow you to remove a person's ability to drink water. They take a sip of the water, and it tastes normal. But the moment you suggest they become 'hypersensitive' to the chemicals in the water, they find it tastes absolutely revolting! They will refuse to take another sip! 

This is primarily a stage routine, but it can be used in close-up situations.

This is a 10 page PDF manuscript.