Subway has decided that the best way to manage the super hot summer is to offer up a big old wiener sandwich. Why go for some cool cold cuts on a bed of veggies when you can eat a hot sausage with cream cheese sauce that weighs in at 445 calories. I'm not suggesting that Subway is always the epitome of healthy eating, but that is the way they sell themselves. I'd think it'd be better to opt for something lighter for summer than a bit of sausage.
Mos Burger, on the other hand, is offering a "lettuce burger" to allow the Japanese market to embrace low carb living. You can substitute lettuce, iceberg, of course, for the bun on several different burgers (fish, beef, chicken, teriyaki chicken, pork cutlet). Though I recognize the nutritional value of a bun is pretty much zero and that this is a better choice from that viewpoint, to me, a burger is not a burger unless it comes between two starched planes.