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Ranieri's side were 2-0 down with 20 minutes remaining before coming back to beat Aston Villa 3-2 last weekend.
Ranieri said: "Coming back from behind might be exciting, but it is not good.
"I told them, if you keep a clean sheet, I'll buy pizza for everybody. I think they're waiting for me to offer a hot dog too."
Leicester are unbeaten after five Premier League games - conceding seven goals - and find themselves second, four points behind leaders Manchester City.
Jamie Vardy, Jeff Schlupp and Marc Albrighton were named as the three fastest players in the division this week, leading Ranieri to compare them to fighter jets.
He said: "I say my team is like the RAF, it's fantastic  - whoosh whoosh! -  I love it."
Stoke, meanwhile, have yet to win this season and Ranieri has warned his side that they will have to work hard to continue their fine start.
"We have to be careful," he said.
"My players have been incredible but I have warned them they can't continue to give teams a start because one day you will get punished.
"There is a very good spirit. They are characters. But I'm very curious - I want to see what they are like when something goes wrong.
"Every man can go to the ground, but I want to see when they pick themselves up. That is my focus."
Leicester manager Claudio Ranieri has told his players that he will buy pizza for the whole squad if they keep a clean sheet against Stoke on Saturday.