First cider

Hey guys, new to brewing and this site. I made a gallon of mead that was... okay, and figured I'd try my hand at something that wouldn't take quite so long

So basically I just threw a gallon of apple juice and some yeast into a carboy and let it sit for a few weeks. I'm going to transfer it to bottles and try it out this weekend

I'm thinking about adding some sugar to the next one to get a higher abv. Any clue around how much I can add without having to wait a stupid amount of time for fermentation to finish?

Also does anyone have other recommendation to make it taste a little more interesting next time?