- Butter a marble slab or line a baking sheet with parchment paper.
- In a saucepan, bring the sugar, water and vinegar to a boil. Add the food coloring when the thermometer reads 120 ° C (250 ° F). Cook until the thermometer reads 143 ° C (290 ° F). Remove from the heat immediately. Work quickly preparing one lollipop at a time.
- Pour about 15 ml (1 tablespoon) of syrup on the sheet. Place a stick at the centre and cover with an additional 15 ml (1 tablespoon) of syrup to secure the stick. Quickly place a few Smarties. Repeat for the remaining lollipops. If the mixture hardens in the pan, gently heat to a pourable consistency.
- Wrap the lollipops in wax paper.