Step 1 In a large, 2-quart glass jar, mash the strawberries. Pour over the vinegar and cover with a non-metal lid. Place in a cool, dark place for 7 to 10 days.
Step 2 Pour the strawberry mixture into a medium stainless steel pot and add the sugar, kaffir lime leaves and a pinch of salt. Boil the mixture for 10 minutes.
Step 3Strain the mixture into sterilized jars and cool.
Step 4To serve with soda water, mix 1 part sweet & sour with 4 parts soda water over ice and serve immediately.