McDonald’s is offering free pickle juice to runners and spectators during the Chicago Marathon weekend. The initiative, called Pickle Boost, provides bottles of the juice runners often use to combat cramps. The first giveaway is on Oct. 9 at 2401 N. Lake Shore Drive.

On race day, Oct. 11, five McDonald’s locations will distribute two bottles each to runners and spectators from 7 a.m. to 3 p.m. These locations are strategically placed along the marathon route. The flagship store at 600 N. Clark St. is near the early race route. Read more trail coverage.

Athletes have used pickle juice to relieve cramps, with studies showing it can reduce cramp duration. However, the exact mechanism remains unclear. McDonald’s has not disclosed bottle sizes or sodium content. Pickle juice will not be available at official aid stations. Related: Women-only trail races aim to boost female participation.

This original Runner World brief is based on reporting from Marathon Handbook. Visit the source for its complete reporting, context and any later corrections.