The yearly fast is held around February or March and is a seven day period of prayer and fasting for spiritual purposes that may also be a detoxification fast for physical benefit. For kids it's a three day period of healthy eating. The details of the fast are up to each individual since everyone will have different needs and restrictions.
Some ideas are to fast other things besides food. Your words, your spending habits, or television and social media are always good ones. Fasting is an opportunity for us to set something aside as holy to the Lord and use the time we would normally spend on that thing in prayer or worship instead. Sometimes we need to reign in our appetites and that's what fasting does.
Another option is to do the Daniel fast--pretty much just vegetables and fruits.
In a group practice you might come together for a "breaking bread" meal or gathering at the end of the fasting period.