Slice cucumbers into 1/4" chips, thinly slice onion, and mince garlic.
Layer cucumber slices, onion, and garlic in sterilized 16 oz mason jar.
Combine in medium pot: vinegars, water, sugar, salt, mustard seeds, celery seed, turmeric, cloves, and ground celery seed.
Bring brine to boil, then remove from heat and allow to cool completely.
Pour brine into jar, filling to top.
Seal with sterilized lid.
Refrigerate overnight for best flavor.