Slice the cucumbers lengthwise, then into half-moon slices that are approximately 3/4 inch thick. Put them in a gallon-sized Ziploc bag. Smash them with the flat side of a meat mallet or a rolling pin until they're all cracked down the middle.
In a medium-sized bowl, mix together the vinegar, sesame oil, soy sauce, chili oil, and sriracha, and whisk until emulsified. Pour over the cucumbers, being careful to either double bag them or transfer them to another bag to avoid any leaks that may have been caused by the smashing,
Seal the bag and put it on a countertop, keeping the cucumbers in a single layer, for two hours, flipping the bag after an hour. They can be served at room temperature or refrigerated for about 20-30 minutes before serving. Drain the bag immediately prior to serving. Sprinkle each serving with sesame seeds right before serving, if desired.
Macros are difficult to calculate due to the fact that most of the marinade ends up being discarded. Assuming that each serving has 1 tablespoon of marinade clinging to it (which is probably an overestimate), macros are as follows: 73 calories, 5 grams net carbs, 1 gram protein, 5 grams fat. This does not count the sesame seeds.