"These actions are not tolerated and the franchisee took immediate action to terminate the two employees involved," the company said.
Another worker was fired for an associated distasteful act.
"This isolated incident is not representative of SUBWAY Sandwich Artists. These actions are not tolerated and the franchisee took immediate action to terminate the two employees involved," a Subway spokesman said in a statement emailed Tuesday to CNBC.
The questionable deeds came to public attention Monday after the Huffington Post republished images from Instagram of self-identified Subway employees misbehaving. One showed a penis at rest on foot-long sandwich bread in what appears to be the restaurant's preparation area. However, he told the Huffington Post that the image was actually taken at his home.
(Read more: That Taco Bell shell licker? Yep, getting fired )
Another employee picture shows a bottle filled with a frozen substance. "Today at work I froze my pee," the caption states.
Subway declined to confirm the workers' names or the restaurant's location.
Other restaurant employees have been fired recently for public pictures of inappropriate work behavior.
(Read more: Golden Corral hit by gross-out viral video )
The obvious question - What were they thinking-actually has an answer, according to the experts.
"Though people have been warned many times about what you're not supposed to do, etiquette on the Internet-a lot of people think it doesn't really matter, it doesn't really count. They often think they are invincible," said psychologist Susan Lipkins. "It's like driving fast or doing drugs. There's a huge amount of denial. They think they are invincible. It's a Superman complex. They think it's not going to happen to them.
"Kids get away with so much on the Internet, when they finally get caught it's a surprise. It's sort of like a thief, they start small," she said.
(Read more: McDonald's finance guide 'insulting' to workers )
The situation isn't that much unlike powerful politicians busted for sexting or frequenting prostitutes, Lipkins said.
"What I think happen to people like [former U.S. Rep. Anthony Weiner] and people who are in power, they no longer see the line, their power has allowed them to do it. They are either unquestioned or able to step over the line," she said.
But as for the fast-food workers?
"I don't think the kids feel powerful in the same way. I think they feel anonymous. I think they don't think they will get caught," she said.
Other factors come into play.
"Teenagers are much more prone to stupid behavior, not thinking before they act," said psychologist Neil Bernstein. "They don't ask: 'What's going to happen if I do this ?'
"I think this is a culture of sensational outrageousness. And online is the perfect venue for expressing that," said Bernstein, who is also the author of "How to keep your teenager out of trouble and what to do if you can't,"
"Just how far are we gonna go ? It's extreme," he said.
-By CNBC's Amy Langfield. Follow her on Twitter @AmyLangfield