Welcome to HBT!
Why do you want to create higher alcohol? We're kind of about making good tasting beverages, not about seeing how much alcohol we can squeeze into a bottle.
Sugar will create more alcohol but it won't taste that good. You get thin, cidery beer when you just add sugar. You can make a well balance, high alcohol beer with more malt extract. You will need to adjust your hops to balance out the higher malt.
You won't effect your bottle or your carbonation if you ferment the sugars out before you bottle.
Batch 1 Brewing
The American Revolution would never have happened with gun control.