My son wouldn't ever take a sippy cup either. We tried for months and he just wouldn't get it. One day out at lunch he wanted my water, so I held my finger over the straw to pick up and put some in his mouth, and he sucked immediately and knew what to do. So I let him try it himself and other than it being too fast for him at first, he had no problems. He was probably only 9 mos or so at the time and supposedly they can't do straws til later, but that was all my son would do.
I like the Munchkin brand. (Target,walmart, etc). They have the flexible straws and are BPA free. I also have one of those dishwasher baskets for bottles (also munchkin) that goes in the top rack with the little flip down straw holders on the sides. I put the straws in those, the tops in the top "nipple" part and the lids in the big part. I never have to hand wash, and I think I have the worst dishwasher in the world. I do make sure to never let milk dry in them, and if it does just soak them for a few minutes. My only complaint is that the straw holders on the baskets start to wear out and I have to replace the baskets every 6-8 mos. But they are only like $4 so the convenience is worth it. And sometimes if you put cold liquid in the cup and let it get to room temp, it will force some out of the straw and leak. They aren't totally leak proof the way some sippies are but they are much easier to clean and we only let water be drunk roaming around the house, milk is for meals.
The straws on the Munchkins aren't hard to suck, they are valveless. I did notice when I first bought them that sometimes they wouldn't separate easily for my son who was still very young. So I would just pinch them and that would break the seal of the plastic sticking on itself.