I suppose that would depend on the convenience store. There are great convenience stores such as Buc-ee’s, Wawa, QuikTrip, and some 7-Elevens as examples. Then there are some non-so-great convenience stores which only offer junk food.
On a long road trip, I often use Pilot, Love’s and Flying-J locations. I guess these are technically truck stops, but the gas is usually found at a lower price than regular gas stations and some of them are extremely nice with great food.