Awright! We know this one! After a long day of doing tec stuff (mixing white electricity and red electricity, stuff like that) what tonic does a man need?
Could be hair tonic if they got a good crop on the sod.
Or a good muscle tonic that you don't have to share with the horse, something IQ&S, which is...Iron, Quinine, and Strychnine (in right small amounts).
But best bet is Gin and Tonics got up by someone who knows they ain't paying for the gin.