Do they make such a thing? I have tried several Nubys and Munchkins and they all leak. It didn't bother me much until I started putting her milk in it. Now I'm always following her around the house wiping the floor.

Baby J is here! Born on her mama's birthday.
11 pounds, 7 ounces and 23" long at birth!
My Bio
Re: Sippy that really doesn't leak?
These are the best: https://www.toysrus.com/product/index.jsp?productId=2401917
My SIL uses them with 4 boys and I use them with my kids! They are GREAT!
***Baby #3: BFP Mother
We use the Gerber Graduates Spill Proof -- and they work. Alex is known to do the windshield wiper movement on his tray when he is finished with his meal...down goes the sippy. We never have any leaks.
https://www.gerber.com/Products/Fun_Grips_Spill_Proof_Cups.aspx?PLineId=60decc66-4b21-45cd-a5ac-fc1fc2cdff10
Our Nubys leaked also. The only ones we've found that don't leak are the Playtex sippys that have the hard spouts.
We use these also. But I get the non-insulated--plus, they are BPA-free!!
We use the Plaxtex Insulator Twist n Clicks and I really like them. We mainly use them for water, but he'll drink milk out of them too when we are on the go.
Mainly he has his milk when he's in his highchair so I use a different cup which doesn't have a valve so that he will drink a little more. I like those too, but they definitely do leak. We use Tilty cups for milk to hopefully ease the transition to a real cup eventually.