Hi Khushi,
I have a few questions. Can you tell me
1)What is your research question and why did you choose fruit flies to answer your question?
2) What are the short-term and long-term objectives of your research project?
3) What is the temperature in your area? Do you think winter temperatures can impact growth and activity of fruit flies? Maybe keep the rotten fruit longer.
You can also try to make Tomato Rava Sugar + Vinegar medium (TRSV) previously made by other CUBEists. Please see this post for details Newly developed home made media for fruit flies