This question is about Cycling
Yes, early evidence suggests that you can drink milk before cycling (specifically low-fat or fat-free milk) without incurring GI distress during a ride, provided you do not have a milk protein allergy or lactose intolerance. Milk provides carbohydrates to fuel working muscles during a ride, protein to support muscle growth, and increased fluid intake to prevent dehydration, all of which can help support performance[ 1 2
Milk is also a good source of calcium and Vitamin D, both of which play an integral role in bone health (which is important for athletic performance) [ 3
3]. Since your body needs vitamin D to absorb calcium and ultimately strengthen bones, it’s important to look for dairy products that are fortified with one (or both) of these nutrients. However, if you have a dairy intolerance or allergy, you should avoid milk. Instead, choose a milk alternative that is also fortified with vitamin D and calcium.
 Dietary Guidelines for Americans 2020-2025. Retrieved from https://www.dietaryguidelines.gov/sites/default/files/2021-03/Dietary_Guidelines_for_Americans-2020-2025.pdf
Haakonssen, E. C., Ross, M. L., Cato, L. E., Nana, A., Knight, E. J., Jenkins, D. G., Martin, D. T., & Burke, L. M. (2014). Dairy-based pre exercise meal does not affect gut comfort or time-trial performance in female cyclists. International journal of sport nutrition and exercise metabolism, 24(5), 553–558.
 U.S. Department of Health and Human Services. (n.d.). Calcium and vitamin d: Important at every age. National Institutes of Health. https://www.bones.nih.gov/health-info/bone/bone-health/nutrition/calcium-and-vitamin-d-important-every-age