I've taken drinks inside Walmart Stores before without anyone telling me I couldn't do it.
I sometimes like to take a bottle of water or a foam cup of soda into the Walmart Store with me to drink while I'm shopping and never had a problem.
And at least at the Walmart Here I've never seen any signs posted that prohibited bringing drinks inside Walmart.
So as long as there are no signs prohibiting the drinks inside the Walmart Store you can go ahead and bring the drinks inside Walmart and the worse that will happen is they tell you that you cannot bring the drinks into Walmart anymore.