Add tomatoes, garlic, peppercorns, and basil to 1-quart-size glass jar fitted with a lid.
Combine water, vinegar, salt, sugar, and crushed red pepper in a small saucepan, and place over high heat.
Cook, stirring often, until salt and sugar have fully dissolved.
Remove from heat just before the mixture comes to a simmer.
Pour hot brine over tomatoes and seal jar.
Allow jar to cool to room temperature, then place in the refrigerator until completely chilled, at least 8 hours.
Best served after 24 hours and up to 2 weeks.
