The pair were spotted by the manager at around 6pm when there was potential a child could have walked in, a court heard.
Police were called and Smurthwaite, 23, of Durham Road, Stanley, and Stamp, 33, of Blackthorn, Coulby Newham, Middlesbrough, were interrupted and arrested.
Now, both men have been fined after pleading guilty to one charge each of engaging in s3xual activity in a public lavatory at Newcastle Magistrates’ Court.
“They have been full co-operative with the police and they’re mortified of having this happen to them - they’re both extremely upset.
“There’s no way they will get into this sort of trouble again. It will definitely not happen again,” the court heard.
Stamp, who is employed, was fined £180 and was ordered to pay £50 costs and a £30 victim surcharge, while Smurthwaite, who is unemployed, was fined £120 and ordered to pay the same costs and surcharge.