HAVANA—Sitting down for Christmas Eve dinner with his family, retiree Tomás Hernández looked forward to a plate of rice and beans, fried plantains, yucca and a bit of stewed pork.

“Basically, it’s what we eat every day. We don’t have anything else,” said Mr. Hernández, who decades earlier fought with the Cuban military in Angola and now struggles to get by on a pension of about $10 a month.

Unlike...