Since I first read this question, I've rewatched the entire run of Sliders. While I can't promise my full attention was on it at all times (the show got very, very bad on occasion), I was specifically looking for the scene you describe (but don't blame yourself, I was planning on rewatching the series anyway).
And, to the best of my knowledge and observation, that scene does not exist in any episode. There is a slim chance it occurred during a moment that my mind wandered drastically out of a desire to protect me from stupid, but I don't believe so, and I paid particular attention whenever they either told someone about their adventures, or needed to steal something. Unfortunately, as transcripts of all the episodes do not seem to exist on the net, it is hard to verify with simple searches, but I'm confident enough to give it as an answer.
I think it's more likely that you are either confusing it with a different show, or misremembering a part of a piece of tie-in media like a comic or particularly well-done fanfic with a scene like this and your imagination filled in enough details to give you a memory of it happening in video form.