S.C.
It sounds like he's just trying out his new learned independance for a run. Also, it sounds like you're on the right track too, although frustrating. My suggestion would be to try to get him to ask you for things. Instead of asking him "do you want juice?" to which he'll reply "I don't want juice" then stand there with the cup until he asks for it. Make sure he sees you pour it and maybe you can take a drink and say "yum, this juice is really good" which may peek his interest. Also, try saying things like "boy, wouldn't it be nice to go play outside? Mommy would sure like to do that, it looks so nice out there" and then mope yourself. He's just testing limits which all children do. But you have to turn the tables a little and get his to lead the way which may be what he looking to do. Get him to make the suggestions and then applaud him for being such a bright and smart boy for giving you the idea. As parents it's very easy to control the day with when it's time to eat, sleep, play, go outside but when kids get to a certain age they want to start being able to control some of the show. Ask him what he wants to do and if he can't tell you then you will do nothing, throw your hands up and say "ok then, we're going to stay here, sit and do nothing." He will get bored really quick with doing nothing and will either be a little stubborn and go stand by the door without saying anything to which you can encourage him to suggest going outside or he'll just start saying "I want" rather than "I don't want."
That's my suggestion anyway. Hopefully it works. Just try giving him a little control with decision making and let him be the one to say it and act really super happy he did. I think that should inspire him. Good luck!