I don’t think there is any way to safely drop 15 pounds in that short amount of time. But I agree with @Neizvestnaya that if you want to lose some weight in that time period, you need to cut out most of the culprits that keep the weight on or add weight.
Cut out anything that has sugar in it (soda, fruit juice, sweetened tea drinks, canned tomato products, condiments, candy, cookies, ice cream, salad dressing, fruit, bread, even yogurt). You can have fruit, but avoid dried fruit which has a much higher sugar content.
Limit your fat consumption, especially the really bad stuff like chips, cheese, hamburgers, hotdogs, cold cuts, red meat, and even dark meat in chicken and turkey (stick to breast meat) salad dressing (again) ice cream (again) milk (except non-fat or skim) and yogurt (except for non-fat plain)
Replace the above items with fresh vegetables, steamed vegetables with no sauces, and anything with lots of fiber (whole grain crackers, oatmeal, whole grain cereal with no sugar added, and water)
Aim for 4 small meals a day. If you limit it to 3 you will get too hungry.
Sample meals below.
Breakfast: small glass of skim milk, coffee or tea with no milk, cream or sugar, small bowl of All Bran cereal.
Lunch: small green salad with romaine lettuce, shredded carrots, sliced radishes, and a few broccoli or cauliflower florets dressed with a squeeze of lemon juice and a grind of black pepper, or a splash of rice vinegar or balsamic vinegar. A half a slice of dry toasted whole wheat bread, large tall glass of fresh brewed iced tea (with no sugar added) 3 almonds (you have to have some protein).
Dinner: small filet of grilled white fish with a splash of lemon juice, small bowl (about a half a cup) of roasted vegetables (any combo of sweet potato, onion, mushrooms, beets, rutabagas, Brussels sprouts, asparagus) one triangle (¼th) of a toasted whole wheat pita pocket, dry, glass of diet soda, iced tea or water with a squeeze of lemon juice.
Evening snack: 3 whole grain crackers like Triscuits or Wheat Thins (make sure first ingredient on the label is whole grain something) no toppings, no dip, no cheese.
Day Two
Breakfast: small bowl of oatmeal (not the instant kind in the pouch which is full of sugar) just the regular kind, like quick cooking oats in the Quaker Oat cylinder shaped box, with ¼ cup of skim milk, no sugar, coffee or tea with no milk or sugar
Lunch: small green salad with ¼ cup total of rinsed canned beans (whatever kind you like such as garbanzos, red kidney, canellini or pinto) with a sprinkle of lemon juice or vinegar and a grind of pepper, the white part only from a hard cooked egg, with a teeny tiny sprinkle of salt, iced tea, diet soda or water with lemon.
Dinner: a very small baked potato with a Tablespoon of non-fat plain yogurt and a sprinkle of snipped chives or green onions, a very tiny piece (⅓) of a grilled chicken breast with a sprinkling of lemon pepper seasoning and a very small bowl (¼ cup) of steamed broccoli or cauliflower. Iced tea, diet soda or water with lemon.
Evening snack: small plate of sliced carrots and celery sticks.
Day Three
Breakfast: small bowl (½ cup) of unsweetened raw fruit (blueberries, strawberries, melon), small glass of skim milk, coffee or tea with no milk or sugar, 1 inch by 1 inch piece of cheese.
Lunch: ½ of a home made bean burrito (made with canned fat free refried beans) with a Tablespoon of chopped tomato and onion on a whole wheat tortilla, ½ of a sliced apple, iced tea, diet soda or water with lemon.
Dinner: small bowl (½ cup) of whole wheat pasta with 2 Tablespoons of fat free marinara sauce, small bowl (¼ cup) of steamed edamame beans in their pods with a small sprinkling of salt, iced coffee with skim milk and no sugar.
Evening snack: 1 X 1 inch piece of high quality dark chocolate
Make sure to fast walk for at least one hour every day. Drink a glass of water in between meals. This diet will not be fun, but it is nutritious and will make you lose weight. But understand that when you go off of this diet, or any other diet, you are likely to gain all of the weight back. The only way to maintain a lower weight is to change your every day food consumption to something that you will like, that is highly nutritious and feels filling enough for you to keep it up over your life time and to engage in regular aerobic exercise as well as isometric exercises and/or weight training.