Sweet potato in a juice sounds unlikely until you try it. It comes out sweet and gently earthy, and the apple and ginger keep it from tasting like a root vegetable. This is the glass I make on mornings when I need something that actually holds me until lunch.
Scrub the sweet potato rather than peeling it. Most of what you want sits right under the skin, so give it a good wash under cold water, trim the ends and cut it into chunks that fit your feed chute.
Core the apples and cut them into wedges. Peel the ginger and the lemon.
Feed the sweet potato through first, then alternate the rest of it with apple wedges. The apple keeps the pulp moving and stops the starch clogging the basket.
Push the ginger and the lemon through last. Stir the juice properly before you pour, because sweet potato settles within a minute or two.
Pour over ice and drink it straight away.
Blender method
Peel the sweet potato and cut it into rough 2cm cubes. Peeling matters here, because the skin turns gritty once it is blended.
Core and roughly chop the apples. Peel the ginger and the lemon.
Blend everything with the 250ml of cold water for a full minute, until there are no lumps left at all.
Pour it through a nut milk bag or a fine sieve set over a jug and let it drain. Press the pulp gently with the back of a spoon, but do not squeeze hard or starch comes through.
Chill it for ten minutes, stir and serve.
Notes
Sweet potato is starchy, and that changes how you handle it. In a juicer, feed it through in chunks alternated with apple wedges so the pulp keeps moving and the starch does not gum up the basket. If your juicer has a small pulp container, empty it halfway.Blending is honestly the better method here. You get a smoother drink and you can strain it to whatever thickness you like. Do not press the pulp too hard through the bag, or you push starch through and end up with something gritty.It separates quickly, so stir it before you drink it and finish it within fifteen minutes. You do not need to sweeten it. Two apples is plenty.