Heat the EVOO over medium-high heat in a large Dutch oven or soup pot. Add the thyme, lemon zest, garlic, celery and onions. Season the vegetables with the celery salt and black pepper. Cook the vegetables to tender, then deglaze with the vodka. Add the spicy tomato juice, stock, horseradish, hot sauce, Worcestershire and canned tomatoes. Bring the soup to a boil and reduce the heat to medium-low. Simmer to thicken and combine flavors, about 30 minutes. Cool and store for a make-ahead meal. Reheat over medium heat.
To serve, while the soup warms up, butter 8 slices of the bread on one side. Build the sandwiches with the Cheddar slices, buttered sides facing out. Griddle or grill the sandwiches over medium heat until deeply crispy and the cheese melts. Using a serrated knife, cut each sandwich into nine 1-inch croutons.
Stir the lemon juice into the hot soup just before serving. Ladle the soup into shallow bowls, then sprinkle with the parsley and top with the croutons.