What to do when wrongfully accused?

My boyfriend was arrested for supposedly driving under the influence of drugs(marijuana) when he didn't even smoke yesterday. Yes, he does smoke weed, but he didn't have any weed on him or in the car. The cop said he had been following him and saw him swerving. He also said he did this to teach him a lesson. His sister was in the penger seat and they made them both get out of the car. They made him take a sobriety test in 4 degree snowy weather and made him balance on one foot while shivering. They claimed he failed. The cop took my boyfriend to the station, impounded the car, and made his sister find her own ride home. You know what he went through in a holding cell, had to pee in a cup, mugshot, the most embarring things. My boyfriend had been driving all day and was really tired after picking his sister up from work at midnight, so obviously he was swerving a little. When his sister went to pick him up from the station, they wouldn't let her take him because they accused her of being under the influence as well, so she had to return with a friend. Is there anything he can do to get the charges reduced or dropped because he really didn't do anything, he was just tired. I know it's obvious he should get a lawyer. Also, his court date is on the first day of cles at the school we go to. Is there anyway to get the court date move. We also live in New York State.