Most likely, a doctor or surgeon is requiring you to follow a clear liquid diet.  However if you are doing this for yourself for other reasons, it's important to talk to your doctor about whether or not a clear liquid diet is safe for you.  Ask your doctor the purpose of the clear liquid diet, how long it needs to last and what exactly you're allowed to consume during that time. Also ask if you should limit physical activity, discontinue supplements or discontinue or change any medications you're currently taking. Ask your doctor to review any potential side effects your doctor may expect you will experience during your clear liquid diet. Once you're clear with what you can and cannot have during your liquid diet, take a trip to the grocery store. They key to success is being prepared; have the right clear liquid foods on hand.  Stock up on the items you're allowed to have so you have all the necessary items at home ready-to-go. It's helpful to have everything you need at home.  It may be hard to follow the prescribed diet if you don't have adequate supplies at home or at work. Stock up on items like:  broth, popsicles, jello, flavored waters, tea, coffee, and clear juices (like apple juice or white grape juice). Clear liquid diets may be associated with some side effects.  It'll depend on what you can have on your clear liquid diet and how long you're supposed to follow it.  Side effects are usually mild and may include:  hunger, headache, nausea, fatigue and diarrhea. Call your doctor if symptoms worsen or if you're feeling sick.  Tell them when the symptoms started and how they're affecting you.

TL;DR in Vietnamese:
Hỏi ý kiến bác sĩ. Đi mua sắm tại cửa hàng tạp hóa. Sẵn sàng đối mặt với tác dụng phụ.