Have you been to jail for that long before? Take plenty of money for commissary and you'll be good on food. Been over ten years since I've been, but $50 a week was good back then. Probably more now I'm sure.
Part of it will depend on the quality of the jail food too. Some jails will feed you a bowl of corn flakes every morning and give you lunch meat and chips every single night for dinner. Some actually feed you real food. You'll want to stock up on instant coffee, stamped envelopes, Ramen noodles, and minutes on phone cards. Things people with no money need and can't get. These you can easily trade for good served food items if there are any. Meat, eggs, and protein in general.
For workouts obviously calisthenics. If you can tie up a sheet between two things you can do inverted rows and pull ups. If you can tie two in a doorway you can hang upside down and do shrugs with your feet propped up on the higher one. Trash bags full of water for weights or tie up books or anything in a sheet for dumbells. Can sit on a top bunk and loop it on the end of your foot for leg extensions. Pretty much anything you can do with a dumbbell. Just have to get creative.
Are you still on the suboxone? If so this would be a great opportunity to kick that habit for good. Jail and prison is how I finally left all that shit behind for good.
Idk about the gear. That's probably gonna suck. A buddy of mine that ran gear just did some jail time and he didn't work out at all and got up close to 300lbs while he was locked. Definitely don't go that route lol. But anyway, good luck.