Back in the old days you could get a decent view of the US Naval base from the 320m-high Mirador de Malones 20km to the east of Guantánamo City, but visits were curtailed in the late 2000s. Now, just off the main road to Baracoa, close to the where the entrance to the old Mirador used to be, is the new Ranchón La Gobernador, a simple rustic bar/restaurant with a lookout tower equipped with strong binoculars.
An onsite multilingual guide is on hand to help you pick out the admittedly distant US installations. And no, you can't see Cuba's only McDonalds.