McDonald’s is putting its own briny twist on marathon weekend in Chicago.

The fast-food giant is handing out limited-edition bottles of “Pickle Boost” to runners and spectators during Chicago Marathon weekend, starting Oct. 9 and continuing through race day on Oct. 11.

McDonald’s said the promotion is inspired by pickle juice’s popularity among athletes who use it when muscle cramps strike during workouts.

Runners can pick up the bottles at a Friday morning pop-up on Chicago’s Lakefront Trail, then at five McDonald’s locations along or near the marathon route on race day, while supplies last.

The promotion taps into a longstanding belief that pickle juice can help prevent muscle cramps, which science partially backs up.

“Pickle juice may help relieve muscle cramps, but the research is mixed,” said Jena Brown, RD, CSSD, a Texas-based sports dietitian and owner of Victorem Performance Nutrition, which works with endurance athletes.

One small study found that pickle juice appeared to help electrically induced cramps subside more quickly than water in dehydrated participants, said Brown, who is a longtime runner herself. But that research did not examine runners during an actual marathon, and another study found no benefit.

“Muscle cramps are not fully understood and are likely not induced by a singular cause for all runners,” she said.

Electrolyte losses may contribute to cramps in some athletes, but pickle juice’s possible benefit may not be as simple as replacing sodium, Brown said. Another theory is that vinegar may stimulate receptors in the mouth and gut and affect signaling between the nervous system and muscles.

The evidence for that explanation is limited, and it should not turn pickle brine into a runner’s primary race-day strategy, Brown said.

“Pickle brine is not a replacement for a hydration and fueling plan,” Brown said.

A typical sports drink supplies fluid and carbohydrates for energy, while a small sip of brine offers little fluid and no fuel, even though it contains electrolytes lost through sweat, she said.

Runners who have tried pickle brine in training may tolerate it well and believe it helps, Brown said. But she cautioned against debuting the sour, salty remedy on the day of the marathon.

“I would not recommend trying pickle brine for the first time on race day,” she said.

If a severe cramp hits and a runner opts to try it, Brown recommends taking small sips rather than chugging it and gently stretching the affected muscle. Runners who are sensitive to salty or acidic drinks should be especially careful, she added, particularly later in a race when heat, fatigue and stomach upset can become bigger concerns.

Fox News Digital reached out to McDonald’s for further comment.