Sandwiches can be kept in the refrigerator for three days. According to the query of Kyushu Drunk Catering Network, sandwiches can be kept in the refrigerator for 3 days if they are placed in a freezer at 3~ 10. If the sandwich is left for too long, it will lead to oxidative discoloration of ham, dehydration and wilting of cucumber, and the ham and cheese in the sandwich are prone to rancidity and bacteria, so it should be eaten immediately after making.