I buy a loaf of 50/50 from Lidl and make sandwiches in bulk for me and my wife which are then frozen.
Ham and mustard, beef and mustard, cheese and mayo, roast chicken and cheese and mayo - all work well with a bit of butter and some salt and pepper. Have a jetboil stove for brewing up on the go but I sometimes grab a real coffee as a treat.
Avoid any vegetable / salad with a high water content as it is bad news when frozen.
Bon Appetit!