In short, cocaine is cut with whatever the manufacturer and dealers want to add to it. This often includes substances that look like cocaine, such as baking soda, flour, cornstarch, and levamisole (cattle wormer). This is to dilute the product so that there is more to sell.
Other cheaper drugs may also be added to cocaine, again to expand the supply. These commonly include caffeine, amphetamine, heroin, procaine, and numerous other drugs that have side effects that mimic cocaine.
More recently, synthetic opioids like fentanyl have been added to the cocaine supply. This has created a substantial increase in cocaine-related overdose deaths in Ohio and nationwide.