The DR refers to the Dominican Republic, not doctor as in the title of the classic Robert Palmer tune. I've gone to Punta Cana on vacation, and my experiences there have been full of leisure and libations. Adapted from a drink recipe at the Paradisus Palma Real, here's how you can be in the Dominican:
2 ounces dark rum (hola Barcelo Imperial)
1.5 ounces coconut water (I prefer Zico)
.5 ounces super simple syrup
Combine in a shaker with ice, stir as if you're doing the bachata, and strain into a chilled glass.
When it comes to Dominican rum, I'm a big fan of Barcelo Imperial. I discovered it at Sanctuary Cap Cana courtesy of a Dominican guy next to me at the bar. Other Dominican rums such as Brugal are good, but Barcelo Imperial is better. You can get it online, and I've even found it a local liquor store or two that occasionally carries it.
For the coconut water, use whatever brand you like. Just make sure that it doesn't already contain sugar, otherwise the cocktail will be too sweet when you add the super simple syrup.
Although the In The Dominican is not as "alcohol forward" as other cocktails in the Den, it is refreshing, delicious, and possibly dangerous. It may make you muy caliente and give someone a bad case of loving you.