As long as its not a carbonated drink, you should be able to "shake" the drink to get the powder to disolve. Stirring never works for me. I ?? why its clumping tho. For some reason that has me concerned, but maybe its just been so long since using the powders. Whenever I make ANY drink from powder, I shake things (even chocolate milk) because I hate the sediment that falls to the bottom. It does make it "foamy" so you might have to let it set a minute. IF you have a whole container of juice, maybe you can add it to the whole container & just give it a fresh shake each time. Of course this means ANYONE who drinks it will get the powder LOL! I am a shaker. Its easy & seems to avoid issues for me.