Wearing gloves, roughly chop the Scotch Bonnets removing the stalks. You can remove the seeds and membrane for a slightly milder sauce or leave them in for full heat.
Add the chopped chillies to a food processor and blitz for a few seconds until finely chopped.
Transfer to a small pan with the vinegar and salt. Bring to the boil then reduce heat and simmer for 5-10 minutes until the chillies have softened.
Add the water and sugar, stir well and simmer for a further 4-5 minutes. Keep an eye on it and lower the heat if it looks like it's catching.
Remove from the heat and allow to cool completely.
While cooling, sterilise your bottle by boiling in water for 10 minutes or heating in the oven at 150°C for 10 minutes.
Once cooled, transfer the sauce back to the food processor and blitz until completely smooth.
Pour into your sterilised bottle, seal and store.