I have the wow cup for DD (2.5 years old) and I LOVE it. It's 100% spill-proof. I just throw it in the diaper bag and go. I can give it to her in the car, on the sofa, etc. and not worry about it leaking. It's great.
I buy the nubby straw cups at walmart. The first few time I took the straw out of the cup and tipped the cup so the water would be in the spout. Once she figured out to suck on the top part/straw I put back the inside straw. She never had any problem with the straw cups. As for the WoW cup they need to be able to tilt they're head back when they lift the cup up that is why they make it for older kids.
Playtex used to make this really cool straw cup with handles that you could squeeze and the water would travel up the straw. But they don't make them anymore
Re: wow cup
We switched to straw cups and he never went back.
https://www.walmart.ca/en/ip/wow-cup-8oz-yellow/6000118330945