John Lightfoot on Luke 23:36

[They brought him vinegar.] Vinegar was the common drink of the Roman soldiers; and hence those to whom the custody of crucified persons was committed had it always ready by them. "He commanded that no soldier should drink wine in their expedition, but that every one should content himself with vinegar."

"The provision this man (viz. Misitheus) made in the commonwealth was such, that there never was any great frontier-city which had not vinegar, bread-corn, and bacon, and barley, and chaff, laid up for a whole year," &c. "Thou shalt give us as much hay, chaff, vinegar, herbs, and grass, as may suffice us."

Hence it may become less difficult to reconcile the evangelist amongst themselves, speaking of wine given him mixed with myrrh, and of vinegar too; viz., a twofold cup: one, before he was nailed to the cross, i.e. of wine mingled with myrrh; the other, of vinegar, while he hung there: the first, given by the Jews according to their custom; the second, by the soldiers, in abuse and mockery. But if you will grant a third cup, then all difficulty vanisheth indeed. Let the first be wine mingled with myrrh; the second, vinegar mingled with gall; the third, mere vinegar: which the soldiers gave to malefactors if they had desired drink, being that which they drank themselves. Hence the vessel filled with vinegar, was always in readiness, that the soldiers might drink when they had a mind, and persons also upon the cross, if they stood in need of it.