It really shouldn't be a problem eating quite a bit more than 700 calories, even with a suppressed appetite. The key is proper planning and management of your diet so you know what and when to eat and make sure the food availble is there.
You mention your appetite is best early in the morning/late at night so it sounds like you take your medication in the morning and its effects last all day. In that case you can have a big breakfast and dinner. Even though it's somewhat better to eat more meals during the day a lot of successful diets -warrior diet, lean gains, IF- are centered around only 1 or 2 big meals.
If your medication is split up into separate doses you can time your meals so you eat right before you take your next dose. That way you can have 3 or 4 meals a day which is completely sufficient. If your medication isn't split up you can still do 2 meals and just rely on smaller snacks/meals.
For food choices you want to stay with calorie dense and appetizing foods. Fats in general are very calorie dense, so foods like nuts, nut butters, heavy cream, eggs, butter, avocado, cheese, fatty meat/fish etc make it extremely easy to hit your calorie goals. An example breakfast could be eggs + meat (sausage/salmon/steak/bacon)/and or cheese, with a piece of toast/fruit and some veggies. That easily can get up to a thousand calories by itself.
Carbs also are a good choice because they can increase your appetite and generally are easy to eat. Things like bagels/flour tortillas pack a lot of calories. Fruit also is high in carbs and make for a great snack -such as oranges/bananas. Its best to stick to whole grains but more processed carbs like sugars/white flour will be easier to eat.
Liquid calories can be used as a last resort if you just cannot get the calories up via solid foods. You can make a meal replacement shake by mixing milk, protein powder, fruits, and peanut butter for example. A modest shake can easily pack ~500+ calories and would be very easy to put down. If you have a sensitive stomach/lactose intolerance look into pure whey isolate/lactose free milk.
The most important thing is to figure out how many calories you should be eating to achieve your goal -sounds like you want to lose fat, so probably around 1500 calories if you are sedentary. Then figure out how many meals you can realistically eat and split up your caloric intake over those meals. Try to make the meals as balanced and healthy as possible -natural/whole foods, no processed foods, vegetables, balanced macro split. And you will be fine.
One last thing to consider is that if you just started on a new medication its possible your appetite will improve soon as you develop tolerance and the side effects are lessened.