Bruges is a beautiful place to spend a day and a hard place to reach in one. It sits about 270 km from Paris, in Belgium, and coach day trips run 13 to 16 hours, with roughly three and a half to four and a half hours on the road each way. The train is faster: Eurostar to Brussels takes about 1 hour 22 minutes, and a direct Belgian train on to Bruges about an hour more.
Our honest advice: go by train and stay a night. Bruges is at its best early in the morning and after dark, once the day-trippers have gone. If one day is all you have, a coach tour takes care of the logistics, and the best-rated one gives you Brussels as well. Every option we could verify is compared below.