A major example is the US drinking age. Federal highway funds, which provide money for interstate highways, major US routes, etc, are partially contingent on states (who are given authority over alcohol laws both by the general police power and the 21st Amendment) setting the minimum age for the legal purchase of alcohol at 21. The National Minimum Drinking Age Act withheld 10 percent of highway funds from states that didn't comply. The fact that it wasn't 100% let the Supreme Court allow it to slide, but eventually all the states did comply, and effectively the US has a drinking age set by the Federal government instead of the states even though the states technically have the power to set an age themselves.
The Federal government using the withholding of funds to get the states to do what it wants is a well-documented phenomenon.