I say quick, and if pushed for time, a few hours might do this, but what I really mean by quick is a couple of days as opposed to a couple of weeks. But if you're planning ahead to make a bit of sushi and you can't find pickled ginger, why not try this? It will only take a few minutes to prepare.
I've just stated 'vinegar' in the list below. I suppose rice vinegar would be the thing, if you could get it, but as this is supposed to be an emergency recipe, we have to say that any vinegar will do. And it will. I've tried it with cider vinegar and the result was okay, but a little tart. I tried white balsamic vinegar, too and that was milder. Use what you've got.
Ingredients
A lump of root ginger
A few teaspoons of sugar
A little vinegar
Peel the ginger and cut in half along the centre. This will make it easier (and safer) to slice. Slice the ginger along it's length, as thin as you can. Stuff the sliced ginger into a cup or a small jar, add a couple of tablespoons of vinegar and a couple of teaspoons of sugar. Leave it to marinate for as long as you can. Before serving, drain the liquid off the ginger.
Here are links to some more recipe ideas for a Japanese-style veggie spread:
veggie sushi
vegetable tereyaki
veggie miso soup
asparagus braised in orange juice
...and here are some more more pickles and preserves recipes.