Try roaming around Indang, Cavite and visit the sugar palm (kaong) vinegar producers. They have the same thing in common, they use large earthen jar (banga) as fermentation vessels for their vinegar. According to their statement, banga is the best fermentation vessel for making of vinegar and they prefer an old heavy banga with thick walling. Most of the time fermenting in other container like plastic tumbler will fail. However, they failed to explain why.
The following paragraph could be the answer. Drop a comment if you want to protest.
The optimum temperature for vinegar fermentation is at room temperature or about 20-22°C. The Acetobacter aceti, the microorganism responsible for the production of acetic acid, can still function at higher or lower temperature but the output will be lowered. In a worse case of temperature extremities, acetic acid production may halt.
During daytime, temperature rises and drops during night time. We all know that earthen jar has a thick clay walling. This thick walling helps maintain the temperature inside the jar so that the vinegar production can continue without temperature interruptions.
Fermentation in other vessels such as plastic tumbler and mineral water bottle could yield the same good results if the rise and drop of temperature can be prevented.