FBW,
I have done a little fasting/asceticism since I am an Orthodox Christian. It can be a great thing but we often focus too much on punishment (especially my Protest and Catholic brothers).
The entire concept is emptying yourself of worldly things that have no value in the Kingdom of God (like excessive food consumption) and filling yourself with God’s grace. This is mainly done through prayer. Hunger reminds you to pray, as well as starves your desire to do bad things. Giving up other activities (social media) also takes you off autopilot and refocuses you on God.
Prayer is often hard for people who “get things done.” Your lifts suggest you are in this group. May I suggest a slight change in perspective- you have the opportunity to pray, it’s not an obligation. Spending time with God in prayer is the best way to improve your relationship with Him.
One last thing: 90 days is too long, try backing it down to 40, a scripturally based timeframe. For 40 days you could maintain your lifts while prioritizing prayer, and helping others in your group. You don’t need to go all the way on the fasting— giving up a few things goes a long way.
Any way you do it- best of luck!