Step 1

Wipe the grill grates with oil to prevent sticking. Build a high-heat fire. Your high-heat zone should have embers 1 to 2 inches from the cooking surface, with occasional flames licking it.

Step 2

Place the lemons, cut side down, over high heat until they are charred and soft, about 3 minutes. While the lemons char, using tongs, hold 8 of the thyme sprigs over high heat just until they start to color and give off wisps of smoke.

Step 3

Add the remaining 8 thyme sprigs to a cocktail shaker, squeeze in the lemon juice, and add a couple ice cubes. Shake very well and strain into a pitcher. Add the ice water, vodka, and agave, and stir until the agave is dissolved.

Step 4

Serve the drinks in ice-filled glasses garnished with a charred thyme sprig.