I have one shy and scared little sugar glider, and one brave and aggressive little sugar glider. Both are opposites yet get along well.

Here's my problem, both bite really REALLY hard when I cup them in my hands in order to get them to calm down. Am I doing something wrong? How do I stop this? Or will it wear off after a 2 days or 3 days after they realize biting when cupped in my hand doesn't necessarily get them what they want. I cup them in my hands because they crab and try to get away to the floor, so I do that and speak to them softly to make sure they know they're secure. Any help and information is highly appreciated And if someone is open to random questions that'd be great!

Since they are still new and don't trust you yet, maybe you should cover your hands with fleece to cup them. I have spare pouches that I use as gloves to protect my hands, and they seem to prefer that too.

Any random questions, just ask away. We are here to learn from each other.

i'm gonna leave them alone for around 3 days, and then handle them daily does that work? will that eliminate the biting after a while?

They bite it's normal. Keep in mind light bites or nibbles are more likely grooming nips and you will need to get used to it.
Hard bites are defensive remember your a giant in comparison and it's usually done out of fear. That being said if you do pull away from them when they bite you are reinforcing them to bite more often as your doing exactly what they want by pulling away.
Start by placing fleese in cage every night with your scent on it (not sweaty) they have great noses and you want them to first get used to your smell. After that use a bonding pouch and carry them around the house during the day when there asleep that will help with trust. Start by just placing your hand into the pouch if they bite make a tsssst sound not too loud mimicking the sound they make when they do it to each other. The tssssst sound is what most people believe is their "back off" sound.
Glider proofing a small area or using a pop up tent and letting them roam around and walk to and on you is way better for trust building as well then try to handle them. Just wait till it's time to trim the nails it still can take me hours to do 2 gliders depending on there moods. Many times I stop and finish the next day as my girl nyx really really hates it.

I would not try to handle them to be honest, I think it is better to let them come to you on their own timing.

With my first gliders, I made the mistake to want to handle them, and the result is that it's been a lot slower than it could have... Basically they became close only after I stopped trying.
What I do now is open the cage and let them explore as they please (the room is somewhat gliderproofed, electric cables and plugs are protected, no sharp objects, no unreachable corners where they can put themselves), and now, they come to me when they want while I do my own stuff, and if I suddenly move in the room, everyone just jumps on me to take a ride.

Thank you guys so much! I took the advice and they stopped biting so hard after a while, now it's just nibbles since both are still really scared of me. Except one has warmed up to me just a bit,

Again, thank you all <3!! I have regained hope!

I'm glad to hear of an improvement! It may take time, but it's time well spent and the reward is awesome.