The 18 Day Diet

 The 18-day diet was invented in Hollywood in 1929 for actress Ethel Barrymore.  It provides about 500 calories per day.  Here is the menu for the first 3 days (source):

Day One Breakfast: ½ grapefruit, melba toast, coffee

Lunch: ½ grapefruit, 1 egg, 6 slices of cucumber, 1 slice of melba toast, tea or coffee

Dinner: 2 eggs, 1 tomato, ½ head lettuce, ½ grapefruit, coffee

Day Two Breakfast: ½ grapefruit, melba toast, coffee

Lunch: 1 egg, lettuce, 1 slice melba toast, tea

Dinner: Broiled steak (plain), ½ lettuce, 1 tomato, ½ grapefruit, tea or coffee

Day Three Breakfast: ½ grapefruit, melba toast, coffee

Lunch: ½ grapefruit, 1 egg, lettuce, 8 slices cucumber, tea or coffee

Dinner: 1 lamb chop, 1 egg, 3 radishes, 2 olives, ½ grapefruit, lettuce, tea or coffee

I think it would be hard to follow exactly, but you could modify it slightly.  Melba toast is just prepackaged dry toast.  Bimbo sells something similar called "Pan Tostado" aimed at the Spanish-speaking market, which is probably the closest.