First things first: assemble your materials. You'll need a watermelon, 750 ml. of vodka, a sharp knife, and a chopstick or skewer. Seeded watermelons are ideal because the air pockets around the seeds allow more space for the vodka to infuse, but seedless is fine, too! Don't forget to wash the watermelon so that when you cut into it, the knife can't pass any bacteria from the outside of the watermelon into the flesh.