Look for a round watermelon (which will disperse the alcohol more evenly) and cut a small, round hole into the rind. A square or triangle-shaped plug might crack the melon. Remove it with a corkscrew.
Break up the pulp inside just slightly with a grill skewer, a wooden spoon handle or anything long enough to make a little room for the booze. You may need to let some of the juice out.
Add the alcohol, by either inserting the bottleneck into the hole or pouring little by little into a funnel. You'll only need about half a bottle to saturate the melon. Replace the plug and refrigerate for a few hours.
What Booze to Use
No need to get fancy. You want to taste the watermelon, not some exotic flavored liqueur. We suggest vodka. Or tequila. Then try serving slices with a wedge of lime and some salt.