Is it against straw cup law to hold milk without leaking? With every cup I've tried the milk just climbs the straw until it pours out of the top. Over and over again. I've used Zolis and Munchkin and Playtex cups. I've squeezed the straw. I've loosened the top. I've tightened the top. I've turned it upside down. I don't know what else to do, and it's driving me CRAZY!