Question

How do ants identify sweets kept in a tin

Answer 1

Ants have a far better sense of smell than humans do, and they can find things by smell even if they are out of sight. ants are  able to identify the sweets kept in a tin.they identify the sweets by their smell.

Answer 2

 Sugar has a slight odor, particularly granulated beet sugar. While all species of ants can differentiate between a wide variety of odors, the smelling range differs from a few centimeters to meters.for the food sources that ants cannot smell from a distance they 'smell' it  by touching it.  So in a way, all the food they detect, they detect it by smelling.