It can be used to add flare or meaning to a sentence. Saying ''With Ketchup'' insinuates that what you are saying carries importance to you or someone else. "He washes his car everyday, with ketchup."
Does not mean the actual sauce most of the time
"I talk serious like I like my snacks, with ketchup," "I just got the new Jordan’s, with ketchup," or "I'll call you later, with ketchup."
It can be used to end nearly every sentence, which is possibly one of the reasons it has caught on so quickly.