Rinse the strawberries and soak them in cold water with baking soda (or vinegar) for 10 minutes to remove any dirt and/or pesticides. Do not remove the green stems yet.
After soaking, rinse the strawberries under cold water and let them dry completely. You can use paper towels to speed up this process.*It's important that the strawberries are dry, because excess water can increase the risk of mold.
Remove the stems and cut the strawberries in whatever shape and size you prefer. The smaller they are cut, the faster the cheong will be ready.
In a clean & air tight glass jar, layer the strawberries and sugar evenly, pushing down to minimize air pockets. You can also just mix the strawberries and sugar together, but I recommend the first way.
Close the lid, then set in the refrigerator for a couple days, stirring once a day with a clean spoon to distribute the sugar evenly.
The cheong should be ready to use by day 2. The longer the strawberries sit in the sugar, the more flavor they will extract. Remove the chunks if there are any left, after 2 weeks.
Notes
Refrigerate immediately to prevent fermentation.
Strained strawberry cheong can be stored in the refrigerator for up to 6 months in a clean, air tight container. Unstrained, it can last up to 2 weeks. If you still have any strawberry chunks left after 2 weeks, it's best to strain it to extend the shelf life of the syrup.
Store in a bottle so you can easily pour it out, instead of needing to use a spoon in a jar.
Never use dirty utensils when mixing or scooping the cheong if you are storing it in a jar. Licking a spoon and putting it back into the jar will cause it to form bacteria, mold, and it will spoil.