to smell a rat = to suspect that something is wrong

All the documents were in order, still I smelled a rat.

To Smell A Rat

 

to smell fishy = to seem suspicious

Something about this deal seems fishy. Why don’t we check all the details again?

To Smell Fishy

 

to stink to high heaven = to have a very strong smell or to be very wrong

The room we were given was tiny, old, and stank to high heaven.

To Stink To High Heaven

 

Wake up and smell the coffee! = pay attention to what’s going on

Businesses that think they can pay no tax in Britain need to “wake up and smell the coffee”.

Wake Up And Smell The Coffee

 

to sniff something out = to discover something by looking for it

It wasn’t until some days later that the public sniffed out the scandal.

To Sniff Something Out