From the ad copy:
Taste.Buds is an amazing mentalism routine. Now imagine this.
You have four cups (with lids) each with a different drink. You turn your back, the spectator drinks from one of the cups and you turn back around. Without any fishy moves what so ever you can instantly reveal what drink they had just drunk.

Important Notes:

• You never handle the cups as the liquid is being poured in
• The cups can be borrowed
• No gimmick, no marking
• NO fishing
• NO Psychology
The method is undetectable to the untrained eye.

This is TASTE.BUDS