Well....unless you can kill the tuber (nut) down deep in the soil.....you will never get rid of it.....
Not laughing.....just speaking the truth.....

Repeated removal of the top growth before the plant develops 4 to 6 leaves will help starve the nutlets.

Depending upon how much you have, hand removal is much more economical than boiling water or sugar.

Here is a link that might be useful: 2 different nutsedges

Sugar is pure power, that's just gonna fertilize 'em. If boiling water can kill pokeweed roots, I'm sure it will do fine on the sedge. Just depends on your patience level and gracefulness for not burning yourself. A tea kettle is a good idea.

The most common "nutgrass", nutsedge growing in lawns is Yellow Nutsedge and along with Purple Nutsedge creates major problems for many lawn caretakers and gardeners. Understanding something about sedges can be of some help in devising a control program and the link jean supplied is a very good one.
Sedges evolved in swamps, bogs, wetlands, and do best where those conditions exist. What I have seen is that where landscape fabric is used Yellow Nutsedge is quite prolific and the stalks grow right through the fabric. Once established these have adapted very well to growing in about any environment.
Any product that will kill these sedges will also kill of any desirable plant that product, including boiling water, touches.

Went out yesterday to check out my experiment and seems the sugar killed the weeds, and the boiling water did nothing but give the weeds more moisture, hence, more growth. Now, do I 'sweeten' up the whole backyard, or lay cardboard/newspapers down to stop the weeds all together....hmmmmmm. Think I'll start collecting more newspapers/cardboard!

Thanks for all your input everyone!

How much sugar are you talking about? How much boiling water? There's nothing I've ever poured boiling water on that didn't die.

For your sanity later, please remove the landscape fabric before smothering with cardboard/newspaper. Sorry this happened! So many stories like this about landscape fabric, and I've seen it many times in person also.

There are recent discussions about smothering here, here.

Adding a picture of the area in question might help you get more specific suggestions.