So someone gave me a sugar glider and he's a few years old but they never bonded with Him so Everytime I try to get him in the bag he bites me. Right now I'm going to try to leave it in the cage that way he can sleep in it so I can just hang it around my neck when it's time but if this doesn't work I'm not sure what to do. Do you have any advice?

buy LIVE mealworms from the pet store, you store them in the refrigerator, and
you slowly teach the glider you are not a threat, KEEP HANDS AWAY SO YOU DONT
GET BIT. Start by using a lid or spoon to feed the glider the mealworm. as he
gets more used to you, you will have to read how he gets the mealie, at first it
will be a wild grab, over time, days or weeks, he should calm down some and grab
the mealie a little slower. feed him at night his awake time and feeding time.
then you will have to try to switch to feeding him a mealie holding in your fingers or from you palm. as he gets used to you, move your hand in SLOW AND LOW. try to pet him in the back leg as he eats his mealie. dont come in with your hand
high and fast like a predator, snake or bird that is trying to eat him.
if you make it this far, you can force the glider to step on your arm, put out the mealie with your free arm or hand in the way, so he has to step on you to get
the mealie.
this method can take many weeks is a slow process with slow advancement to get
the glider comfortable, as soon as he seems ok with you more to next step. your final step with have him step all the way on your arm to get the mealie and then he stays sitting on your arm eating, while you pet his rear legs.
you can also put him in bonding pouch and have him with you for short times during the day, at first I would keep this time short, unless he just sleeps then you can keep with you longer.
every glider different, some tame fast, some very very slow.