This is your own personal preference. We prefer carbonation drops as it is much easier to measure.
Here is more information to help you choose:
Carbonation Drops:
Carbonation drops are simply balls of boiled hard sugar. They make carbonating bottles nice and easy as you can just pop them into a bottle without measuring. However, these are designed for 330ml and 750ml bottles so other sized bottles will require you to cut them into smaller pieces which may present challenges. If so, you can use sugar instead.
Sugar:
As mentioned, you do not have to use carbonation drops, sugar is fine. And it can be just plain white sugar at that.
Conversion Chart:
Bottle Size | Carbonation Drops | Grams/Ounces | Teaspoons* |
330 ml | 1 drop | 3.6 g/0.12 oz | ~ 1/2 tsp |
500 ml | 1.5 drops | 5.4 g/0.19 oz | ~ 1 tsp |
750 ml | 2 drops | 7.2 g/0.25 oz | ~ 1 1/3 tsp |
*For measurements in grams - a cut teaspoon of sugar is approximately 4.2 g/0.15 oz
Over & Under Carbonating and Storage:
It is important not to over carbonate as it could be dangerous - this will cause a build up in pressure and could cause lids to pop off and harm someone standing nearby.
Under carbonating will mean it might be flat. If you're certain you measured correctly and it's still flat, check your lids were on and sealed properly/tightly so no gas can escape.
During Storage - Make sure that the bottles are stored at room temperature, away from direct sunlight during the carbonation process.