That is pretty much what I will be doing, should be far easier and my split into 200ml of water will give me 5ml fluid per dose.
How much sugar do you normally mix with 200ml?
I usually do 12L batches so I dont actually mix 200ml of water, I use an appropriate amount of water for the batch size I'm bottling.
So if its a 12L batch I would typically assume a bit extra just in case, so I recently made a Porter and made a solution of 78g of table sugar and topped the water up to 125ml.
To calculate it easier if you use Brewfather, (this is what I use), or similar it will tell you the amount of sugar required for the bottling volume that you have. So for example
My porter had a bottling volume of 11.68L and brewfather said I needed 73g of table sugar to reach 2.4 volumes of CO2.
First I work out the concentation of sugar to wort in g/L
73g / 11.68L = 6.25g/L
Then to work out the volume of sugar solution required you simply take the bottling volume of 11.68L and times by 10 to get 116.8ml, (what you should actually do is take 11680ml and divide by 100, but you get the same answer by multiplying the bottling 'litres' by 10 and taking the anwser as ml). Remember that you are not adding 116ml of water, you are topping up to the volume to 116ml.
Then use 5ml of solution for a 500ml bottle or 3.3ml for a 330ml bottle etc
As someone mentioned above it a good idea to make slightly more solution just in case you squeeze an extra bottle out of the FV.
So to do this I add an extra 500ml to the bottling volume so that makes a total volume of 12.18L so the maths go like this.
73g / 11.68L = 6.25g/L Concentration of sugar required
11.68L + 0.5L = 12.18L Total bottling volume
12.18L x 6.25g/L = 76.125g Weight of sugar required
12.18L x 10 = 121.8ml Volume to top up to
I have it all in a spreadsheet if your interested? I have made an easier to follow version here
Carbonation Spreadsheet