Note: nutrition information was taken from the restaurant's website. All sandwiches below are served on english muffins.
STARBUCKS:
Classic Sausage, Egg, and Aged Cheddar: 440cals, 23g fat, 9g sat fat, 790mg sodium
Peppered Bacon, Egg, and Aged Cheddar: 390cals, 19g fat, 8g sat fat, 830mg sodium
Reduced-Fat Turkey Bacon, Cholesterol-Free Egg, Reduced-Fat White Cheddar: 350cals, 11g fat, 4g sat fat, 810mg sodium
DUNKIN DONUTS:
Egg & Cheese: 310cals, 13g Fat, 5g sat fat, 1,080mg sodium (the one on a bagel is virtually the same. They call the english muffin version a "smart choice" because they compare it to the sausage, egg, & cheese sandwich)
Ham, Egg, & Cheese: 510cals, 15g fat, 5g sat fat, 1,400mg sodium
Bacon, Egg, & Cheese: 360cals, 16g fat, 6g sat fat, 1,310mg sodium
Sausage, Egg, & Cheese: 530cals, 31g fat, 11g sat fat, 1,620mg sodium
MCDONALD'S:
Egg McMuffin: 300cals, 12g fat, 5g sat fat, 820mg sodium
Sausage McMuffin with Egg: 450cals, 27g fat, 10g sat fat, 920mg sodium
Based on this information, your healthiest on-the-go options are:
McDonalds Egg McMuffin
Dunkin' Donuts Egg & Cheese
Starbucks Reduced-Fat Turkey Bacon Sandwich