I try not to. If I didn't bring enough water, there are fountains. I don't ride long enough to need to eat before I get home.
But that's not always possible. There's a Starbucks on one of my routes - mediocre coffee, but frequented by cyclists, there are always 10 people in kit sitting around outside. Bikes don't get stolen there. There are a few Indian restaurants with outdoor seating, they let me lean the bike against my table. This is only an option at the end of a ride. The last time I went into a convenience store, I took the bike in, and the guy wanted to know what my Garmin was. He went in back and hot his wife and pointed at my bike, telling her it has satellite navigation. I thought I wouldn't be allowed in with it, it was a good experience.