I wouldn’t want to dilute it at all. Can you measure well enough to add the sugar directly to the bottles? Or measure the amount of beer you want to bottle and add the sugar before filling?
I have used the carbonation drops that are pills a little smaller than aspirin just dropping three or four into each twelve ounce bottle (depending on the style) and then capping. These are not Cooper’s brand, as seen in the links when I google carbonation drops. I’ll have to see what brand they are when I get home.
Edit: here they are: Web Page Under Construction
Munton’s Carbonation Drops
Something similar to Oscar, I’ve got a few 1/2 gallon growlers so I keep the excess in one of those, then top up the keg after I;ve started pouring. I give it a few days to re-carb but no biggie. Some might say its a waste of CO2 to vent kegs like that, but I inherited a full size 75lb’er, so I’m set for a few years!