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Bit of honey also works (tip from the ridiculously good Bon Appetit 'No knead' focaccia)
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The yeast has no problem using starch for energy. There are enzymes (amylase) that break the starch up into sucrose, so adding it is totally unnecessary. The only difference I am aware of is that added sucrose can be useful to give dough some color when cooking at lower temp in conventional ovens.
my 2 cents
there's no need for sugar. plenty of sugars in the flour. warm water, enough salt, good flour, warm room, 2 hours prove.