The grilled chicken sandwich is the fried chicken sandwich with the crust deliberately removed, and that single subtraction changes the entire structural problem. There is no breading to keep crisp, so the build is no longer a defense of a coating. Instead the design brief becomes the opposite one: a lean, fast-cooking breast has almost no fat and no shell to hold moisture, so every other component exists to keep it from reading as dry. A marinated grilled fillet on a soft bun with lettuce, tomato, and a creamy sauce is not a lighter version of the fried build; it is a different sandwich solving a different failure.
The craft is in moisture management from the grill to the bun. The breast is usually pounded to an even thickness or butterflied so it cooks through fast over high heat without the outside drying while the center catches up, and a marinade or brine is doing real work because there is no batter to seal in juice. The char from the grill is the flavor headline the way the crust is on the fried version, so the heat is high and the cook short. The sauce, mayonnaise based or a sharper aioli, is applied to the bun on both faces, where it does double duty: it seasons and it insulates the bread against the moisture the hot breast and the tomato release. The lettuce and tomato are the cool, wet counter to a dense piece of muscle, and the bun is soft on purpose so it compresses to a flat fillet rather than fighting it. This is a flat-top and chain-counter sandwich, the breast often marinated in bulk and held so it can hit the grill to order.
The variations are mostly toppings and marinade. A teriyaki or barbecue glaze rebuilds the flavor around a sweet lacquer; a bacon and Swiss build adds fat the breast lacks; a Buffalo version borrows the wing's hot sauce and blue cheese; a club-style stack adds a third layer. The wider chicken sandwich shelf, the fried chain icons, the Nashville hot build, the Korean-American style, runs the crust the grilled version drops. Those deserve their own articles rather than being crowded in here.